I don't think anybody answered this yet so...
At MK, AAA parking is to the right of the handicapped parking. It's a little bit of a hike, but not bad.
At the Studios, they always seem to move AAA parking. Sometimes they'll just put you on the end of a row for easier access, but you sometimes have to take the tram depending on when you get there.
At Epcot, I think it's the 2nd row of parking near the kennel. There is a front parking lot that isn't used, so actually it's the 2nd row behind that.
Hope that answers some of your questions.