All good advice from benson though in Florida you won't have to worry too much about condensation. I also wouldn't rip up the floors if they're concrete now but you would have to put down rubber mats on top of the concrete for traction and cushion. IF that's the case go with the 3/4inch interlock mats. They cost a little more than the non interlocks but they won't shift on you. Not much worse than having to redo a stall with mats where the shavings have worked them selves under the mats and then the edges rise up and you have to redo the whole stall. At 100lbs each the mats aren't a lot of fun to work with.
I'll ditto what Gerald said. No worries on condensation and the concrete isn't bad as long as you use stall mats and lots of sawdust. I would worry more if they are going to be on it 24/7 though.