South Carolina SR3 and SR125 sorta follow the Savannah river north. Nice scenic and quiet ride. Ga SR23 and SR24 are nice also. You can go up in one state and back in the other. Any roads between Savannah and Augusta will take you through some real pretty country.
I echo Tank and Jack's comments.......squares are very historic and River St. is awesome. Wish I had my bike with me when I was there.........great places to eat. and Forest Gump too.