We used to do some FL state parks and found that anything along either coast and the Keys were booked at the 11 month mark. We lucked out our first year and found someone on this forum that was cancelling 2 weeks at Oscar Scherer SP and we took 9 days.
We found better luck looking for parks in the middle of the state. Highland Hammocks SP near Sebring was fairly easy to get into. Also, Lake Louisa SP near Clermont wasn't too bad, but the full hookup sites filled up quickly.
We did find some county parks that offered full hookup sites on the Atlantic side, but we haven't done them in about 3-4 years.