I fly T2 and T1 since both WN and DL serve my route and T2 doesn't have much of a line, although I may not be the best expert since I always fly evenings. TSA security lines are usually nil though as noted the Mexico bank may change things. Even for T2, I always arrive an hour early. If there's ZERO line to return the car, you could probably get away with a 6 am dropoff but I wouldn't do it...too many things that can go wrong. I'd do what the others have suggested.