Stealth camping in Florida can be challenging but I've found many also. You've gotta get off the main roads, away from the shore-line, between towns. I never wait till dark, late afternoon or early evening is what I do. I just look for a place where its secluded.
On tour I mostly stealth-camp but, I will mix in pay-sites, of which there are many in FL. I look to average out my costs. It's sad that they wanna charge the same $35 to one-guy-over-night-in-a-tent the same as family in an RV, but that's the way it works. Pay once every 3-4 nights is $10 average...not too bad.