I live in downtown Atlanta and do not drive a car. I do have a scooter though, which makes transport convenient, but before that I walked and used MARTA. Atlanta's vast sprawl does rely heavily on cars, but in the 8 years I've lived here (6 of which were downtown), I have found that not having a car is only a deal-breaker if you live outside of the Perimeter (I-285). If you live/work/learn/shop downtown, MARTA is much more accesible. And in the event that you NEED a vehicle for some reason, Zipcar memberships are available.