I live in an Atlanta suburb so have to do this a lot. I agree with others who recommend that staying on 75 through town is easier than taking the bypasses. Just don't drive in the right two lanes - you can be caught in an exit-only lane in a few places, notably near the old baseball stadium and I-20 interchange as you approach downtown.
Try to plan to be here in mid day - after 10-10:30 AM and before 3:00 PM if passing through in the daytime. Rush hour stays late in the morning and starts early in the afternoon!