My son got his BA in Psychology at CMC and took psychology courses at Scripps and Pitzer. (He took other courses at Pomona.) It is extremely easy to take classes at the other 5C’s as it is one course list at registration and the classes are quite close. On the other hand, you’ll need to take into account the time needed for you to get from one campus to the other - which will take a bit more time. Even the Pomona campus is quite large and you’ll want to schedule classes with plenty of time in between.
I agree that you should do everything you can to live on campus Freshman year - especially at a college like Pomona where 95% or more (I’m pulling this out of a hat) of the students live on campus all four years. California, in general, is very good about access & accommodations for those with disabilities. The Center for Independent Living started at UC Berkeley.