If you are parking around/near the Dome there are several lots about. Parking should not be more than $20. There are a number of lots to the Centennial Park side of the Dome and it is only about 1/2 mile walk to the stadium. The GA Aquarium may also have parking available.
Be Advised: Dragon Con is going on downtown this weekend so give yourself extra time to get to the game. If you do not know what Dragon Con is you will have to Google it. If I attempt to explain it, I will likely put a gun to my own head.