When we drove down, we found the cheapest gas at Exit 5. It was a Pilot Station and was $2.43/gallon, much cheaper than anywhere else. On our way back, we stopped there and it was $2.65, still cheaper ...
We went to gasbuddy to find the prices. I'll have to check out that other website that was listed.
ETA: It was a bit south of Valdosta. Lake (something-or-other, or Twin Lakes, etc. It had Lake in it) ...