In order to get access to the AAA parking, you need to book your vacation through AAA. (It may even have to be a vacation package, I'm not sure) Simply being a AAA member is not good enough, nor is booking a room-only reservation with the AAA discount through Disney's reservation line. It *has* to be booked through AAA.
The AAA parking (and access to it) is a separate matter from the parking fee. It only applies to your parking once you get INTO the parking lot. You still have to get into the lot, whether for free as a Disney resort Guest or Annual Passholder, or by paying the daily fee as an off-site Guest.
But be aware that sometimes the AAA parking isn't exactly as convenient as you'd think. At the TTC/MK parking, the tram doesn't stop at the AAA parking area. You have to walk into the TTC. While it's one of the closest parking areas to the TTC itself, the regular parking areas could possbly be deemed "more convenient" because you can get a parking tram right from the end of your row.
-Rob
-Rob