What type of site are you looking for?
Last winter, we were in Florida from mid-Jan to mid-March, and didn't begin making reservations until December.
First, we spent two weeks in Big Cypress National Preserve. Four days were at Midway C.G. with electric hookups. The rest of the time we were in Monument Lake C.G. with no hookups.
Next, were four weeks in Everglades National park. We had ten days at Flamingo C.G. with electric hookups, and the rest at Long Pine Key with no hookups.
Our next stop was two weeks in Ocala National Forest, followed by two weeks in Apalachicola National Forest. Neither of them had any hookups, but we also had no trouble getting sites with no reservations.
If you don't mind running a generator for a few hours a day to keep your batteries charged, it can be done, even with late planning. IAs usual, I heven't yet started to make plans for our late summer / early fall trip to S. Dakota, Montanna, and wyoming.
Retired electronics engineer. Avid paddler & birder.
2011 Silverado 2500HD, diesel, 4x4,crew cab, 8' bed
Palomino Puma 253FBS (27' 5er) & '94 19' Class B