Don't want to be the wet blanket, but it is highly unlikely that you will just happen to find a spot at any Florida state park campground this time of year. While they take walk-ups, most if not all, do not reserve any walk-up sites. You have to reserve through
Reserve America to ensure a spot. If you don't have a spot reserved, you will want to have a solid plan B because you are likely going to need it. Of course, I'm exactly the opposite. I want to know I have a spot and I don't even really like the places where you don't reserve your specific site.