You have to purchase a Disney package from AAA to get the pass (it's not just open to all AAA members). I have heard of some people getting the pass by just purchasing tickets at AAA, though. I've never actually gotten to park in the lot, but be aware it's only at the MK. I think at the other parks, you get priority to park at the end of the aisle near the tram stops, but I'm not 100% sure on that.