Decent budget-friendly FHU RV parks in Florida?

There are a lot of decent FHU parks on the coast but as has been mentioned, the better and safe ones are booked. You can always call the parks and ask if there are any cancellations. I dont know what your budget is.

In your position I'd take a map, pick out likely FL coastal towns/cities and input their names at http://www.woodalls.com/ as a quick search. Then I'd choose the most likely candidates and start the calls.