There isn't a bubble in the sense that WDW has a bubble, though I question the notion that WDW's bubble is perfect when there's now a giant off-property ferris wheel visible from the Magic Kingdom monorail (at the very least, it was unmissable in 2021, when I last visited WDW). But I digress...
If you stay at a Disney hotel, you can have a reasonable approximation of the Disney bubble, especially if you stay at Grand Californian.
Within the parks, Disneyland has a berm and is very well insulated from the city. You will not see outside the Disney bubble within Disneyland Park unless you ride the monorail, at least in part because Anaheim agreed to certain height ordinances within the vicinity of the park (during a time when Disneyland the park existed but far before Disneyland the Theme Park Resort was a gleam in anyone's eye). At DCA, most of the park is similarly insulated, but owing to the fact that Anaheim was far more developed by the time DCA was built, you will see the city from taller attractions and Pixar Pier (particularly near the point where the midway crosses Incredicoaster's launch track). Downtown Disney is pretty well insulated-at one point you do cross a bridge over a normal road, but the bridge is designed in such a way that many people may never notice.
Outside the parks, Anaheim is definitely a city. Not necessarily an unsafe one, mind, but if you stay offsite and enter the resort through the Harbor Blvd pedestrian entrance, you will almost certainly see homeless people, street vendors, and occasionally protestors. While this isn't necessarily something anyone wants to see, generally speaking if you don't bother them, they won't bother you. They are more or less limited to the area between Harbor Blvd and the Disneyland Resort entrance sign, a fairly limited plot of land all things considered.
But ultimately, you have to decide for yourself if the bubble is important enough to outweight the experience of the actual parks, which is what you are ostensibly there to experience (and I cannot emphasize enough that unlike WDW, there's really no reason to go to DLR if you're not going to the parks). I'd argue that there's enough the parks do right that they're worth experiencing at least once for a few days. Don't miss out on a great trip over something as relatively inconsequential to many of the people who do enjoy Disneyland as a bubble (that DLR never really promised anyone to begin with).