We've discussed it before, and well, South Florida would be very empty (in 1860 there were 7,077 people in the southern 6 counties, about mostly in Hillsborough and Monroe, with 2900 of them just in Key West) while the northern part of the state was just very rural by the standards of the day. And without the Cubans coming into Tampa, and Railroad tycoons like Flagler, The East Coast and South Florida (excluding the Keys and Cape Sable) will likely not develop at all.
But Key West? The Island imports everything but fish, water and air. It's also extremely wealthy by any standard at this point. It did drive development of Cape Sable though, which sold vegetables, fruit and charcoal to the Keys, and Fort Cross was there to discourage a semi-overland raid on the Keys.
The Northern Part of the State is fine if you can deal with Malaria and other mosquito borne diseases, like the South Carolina Lowlands, and would probably be an eclectic mix of loggers, smallholders, ranchers plantation magnates, and the occasional person doing Peat mining in the Okeefenokee, and would be well integrated with the rest of the CSA, (by Confederate standards.)
South florida OTOH would be more or less accessible only by sea, since the Carriage roads were terrible, and a storm like Debby would wash them out pretty easily.