I'm in Atlanta for undergrad now but I go through Athens quite a lot - it's somewhat bike friendly, but I'd definitely plan on getting a car. Georgia as a whole is a very car-based state, and you'd miss a lot being tied to bikeable distances and bike-friendly roads.
Athens is a great town, and lots of fantastic music, great bar scene, etc, and on the scale of georgia it really isn't too far from Atlanta, which opens pretty much every resource you'd want.