I hope you haven't left yet. (And that you have a great time).
We just got back on Wed night. MK was very busy each time we went, but the other parks, not bad at all.
The GAC we had allowed us to use alternative entrances (which would allow a wait somewhere other than in the regular line). We only used it when the wait in the regular line would be 15 minutes or more and we did get fastpasses when we could rather than use the GAC. We showed that GAC to the first CM we came to and were pleasantly surprised to see they all know what to to. The new GACs have a picture that indicates to the CM what type of assistance is needed - much easier than the old GAC we got last year that had a lot of writing on it. In some lines we were allowed access thru the fastpass line - in others we were given a slip of paper with a return time equal to the current wait time in the regular line.
I know the GAC doesn't work for the character greeting lines, but otherwise, you can pretty much use it at all places. Exactly what happens at each line depends a little on the ride, but the CM closest to the entrance can help you with that.
There are some rides (like Pirates, or shows, like It's Tough to Be a Bug) that you have to walk thru the whole line anyway (the fastpass line is no shorter distance). At Alladin's flying carpet and Triceraptop Spin (similar rides to Dumbo), we entered thru the exit and waited there in a quieter spot for about the time we would have been in the standby line. The lines for those looked long, but the waiting time posted for the standby line was still only 10 minutes. Waiting times varied a lot - we never got on the Jungle Cruise, but once when we went by, the standby line was 15 minutes and a little later it was 35 min.
Each park has a status Board that lists current wait times for various attractions. The CMs at those can be very helpful with figuring out what is not busy and the best times to go.
