If you don't like crowds, try the Florida Panhandle. Two years ago (February), we spent a week in a national forest camp ground in the Apalachicola National Forest. Except for one night, we were all alone.
We went back last winter and were surprised to fing a campground host there. Oh well, two units in a campground still isn't very crowded.
The temperature there will not be as warm as in the southern part of the state, but still, quite comfortable.
2011 Silverado 2500HD Duramax, 4x4, crew cab, long bed
Palomino Puma 253-FBS, 27' 5th wheel
1994 19' Class B on Chevy chassis