...So I just learned something valuable ... dialing in the negative EC, 'told' my camera to keep the ISO low...
Lesson learned? Double check the settings,
don't use auto ISO in broad daylight, and don't be afraid to use/apply -EC to get better shots when the sun is shining brightly above. ETA: Oh yeah, 1 more lesson learned - try using Spot Metering. So in a bright situation like the blown out sky, if in Spot meter mode, do I meter off of the lower light areas? Because won't that make the sky more blown out?
You're on the right track, but I'd like to address a couple of points. Specifically, I want to talk about about why your idea "dont' use auto ISO in broad daylight" isn't really correct, and I want to correct you on why spot meting lower light areas would make the problem of blown out skies worse, not better (and why it doesn't matter).
As you figured out, the camera's built-in meter isn't perfect and, left to its own, it will often overexpose parts of the scene (like the sky). To avoid this, it's important to understand the camera's built-in meter and its different metering modes. The camera's meter thinks that correct exposure is when the scene is not pure white or pure black, but, rather, 18% grey. The three primary meter modes are spot, center-weighted, and matrix (evaluative). Spot metering samples a very small part of the frame (usually right in the center focusing spot) and the camera's meter tries to adjust whatever settings it can to expose that spot as 18% grey. Center-weighted metering looks at the entire frame, but gives most importance to the center part of the frame and tries to render the scene as an average of 18% grey. Matrix (evaluative) metering looks at the entire scene and tries to expose it as an average of 18% grey.
So, if you're shooting in shutter priority, you set the shutter speed, and the camera will choose the aperture that it needs to achieve what it thinks is proper exposure (18% grey). When you shoot in aperture priority, you set the aperture, and the camera decides what shutter speed it needs to achieve what it thinks is proper exposure (18% grey). When you enable Auto ISO you provide the camera with one more setting that it's allowed to control in order to achieve proper exposure. So, as you see the problem isn't auto ISO, it's the camera's meter. A camera is just as likely to overexpose (blow out the sky) whether you used Auto ISO or not. If you took a picture of a scene without ISO, and the camera blew out the sky, then you took the exact same image with auto ISO enabled, the second image would be overexposed exactly like the first image. The only difference might be that the lower image might have a lower shutter speed and a lower ISO (and be blurry), while the second image would have a higher shutter speed and a higher ISO (but would be sharper).
When you enable Auto ISO you also tell the camera when it's okay for it to raise the ISO and what is the maximum ISO that it should go to. For instance, you may set the auto ISO to kick in only if the shutter speed is about to go under 1/60 second and to only go up to ISO 1600. Your reasons for choosing those settings may be that you want to try to keep the shutter speed over 1/60 to avoid blurry pictures, and you don't want the ISO to go above 1600 to avoid a lot of image noise.
So, let's say you're shooting in aperture priority and set the aperture at f/5.6 and the ISO at 200. Let's say that the camera's built-in meter thinks that the shutter speed necessary for correct exposure at those settings is 1/15 second. If you have Auto ISO enabled to the settings I previously mentioned (kick in at 1/60 and max out at 1600), here's what the camera would do in this situation. It would lower the shutter speed, but auto ISO would stop the shutter speed from going any lower than 1/60, which is about 2 stops under where the camera meter thinks it needs to be (again, 1/15 second). Next, it will try to make up those 2 stops by raising the ISO to ISO 800 (2 stops above ISO 200). So, if you hadn't used auto ISO the shutter speed would have dropped to 1/15, and your image would have been blurry. But, because you used auto ISO, you were able to achieve the same good exposure (according to the camera) while keeping a shutter speed fast enough to keep the image sharp.
Now, let's say that you took a different picture with the same settings above (Aperture Priority, F/5.6, ISO 200, Auto ISO set to kick in at 1/60 second and to max out at ISO 1600). This scene is darker than the previous one, so the camera's meter thinks that in order to achieve correct exposure at f/5.6 & ISO 200 the shutter speed needs to be a slow 1/2 second. The camera will lower the shutter speed, but Auto ISO will stop it from going any lower than 1/60 sec. Since 1/60 sec is five stops under 1/2 sec the camera will try to increase the ISO by five stops. In this case, auto ISO can only make up three of the five stops, because you set Auto ISO to max out at ISO 1600 (3 stops over ISO 200). Only then, in order to make up the remaining two stops, will the camera lower the shutter speed below 1/60. Since Auto ISO was able to make up for 3 stops of light by raising the ISO, the shutter speed only needs to drop two stops below 1/60 to 1/15 second. In this example, if you hadn't used ISO, your shutter speed would have been 1/2, which would have surely resulted in a very blurry image if you were hand-holding the camera. By enabling auto iso, your shutter speed is still very slow (1/15), but it's possible (especially if your lens has Vibration Reduction and your brace yourself steady) to hand-hold at this speed and have an acceptable image. The only trade-off is that you might have a little more image noise, but a noisy image is better than one that's blurry beyond all recognition (at least you can clean up noise).
Okay, so if auto ISO won't cause or prevent blown-out skies, what will? A couple of things. First, negative exposure compensation helps. When you apply exposure compensation you're forcing the camera to expose a certain number of stops (or fractions of a stop) above or below what the camera thinks is correct. Since, as we said earlier, the camera had a tendency to overexpose, you might want to apply negative exposure compensation, so the camera will expose a little darker than what it thinks is ideal. Something else you can do is learn how to use the different metering modes and learn what you should meter to achieve correct exposure. If you used spot metering and metered off of the sky, then the camera will try to expose so that the sky is 18% grey (in terms of lightness/darkness, not color). The problem is that if the sky is not really 18% grey, but it's brighter, then everything else in the scene will be underexposed. So, if you spot meter the sky and the sky is really one stop brigher than 18% grey, you would also dial in one stop of positive exposure compensation, so the sky will expose accurately and so will everything else.
All this being said, you need to understand that very often the difference between the brightness of the sky and the darkness of the everything on the ground is so great that it's just impossible to render both the sky and ground correctly. In these instances, when you try to avoid having the sky blow out you inevitably cause the rest of the scene to be underexposed (too dark). In most instances, especially at Disney, what's on the ground is more important than the sky, so it usually makes sense to just expose for the ground and let the sky blow out. Think about it: you're taking a picture of your child standing in front of Cinderella Castle...what's more important, being able to clearly see your child & the castle, or a blue sky with the important stuff in very dark shadow? It's perfectly acceptable to blow out the sky in order to get the rest of the scene to expose correctly. Another good solution, when nature gives you a sky that's too bright, is to change angles and/or zoom in so your subject fills the frame, thereby minimizing or completely eliminating the sky from the image.
Okay I guess I was way off the mark on that one! Thanks UK! I do have Understanding Exposure and I've read it like 3 times. I guess it's not sinking in.
aaarrggg...
So I just learned something valuable re: using negative EC when it's really bright. I'm certain I had the Auto ISO on as well as negative EC because like I said I had just gotten of HM and didn't change anything. (We were going to DCA because my son wanted soft serve ice cream that they sell there.) So for some reason, dialing in the negative EC, 'told' my camera to keep the ISO low. 
