The issue with MARTA is not of concern when you are departing, but may be depending on when are you returning? If you are returning on a late night flight I would avoid MARTA like a plague. As for parking on 11/27, I would recommend that you try and park at the airport (listen to AM 1120? as you get close) and if there is no parking available cruise on out Camp Creek Pkwy and pick the first park-n-ride that has availability as others have suggested. If you make it all the way to I-285 with out a place to park, take 285 South to Riverdale Road and head North back towards the airport. Look for signs to the Georgia International Convention Center, park in the hotel parking lot, and tip the bellman $20 to get a hotel van ride to the airport.