Officially, yes you have to book your trip through AAA. Unofficially, it depends. Some give it to you if you buy passes. In my case, I booked a trip to US/IOA and asked if I could have one (in case I wanted to go to WDW).
At MGM, the parking is a the end of the rows so you are close to the trams.
At Epcot, after going throgh the tolls, do NOT follow the parking signs. There will be a small sign on your left and it says to follow the green? line for AAA parking. It gets you to the second row left of the monorail station.
I am not sure about AK.
Ed