We've spent the last 4 years cruising SW Florida waters in the winters. We have a 5.5 ft draft
and have had no problems -- just have to pick the places you can go versus some you cannot. There are plenty of places we can go that the limitations aren't generally bothersome. Having said that, two things -- first, when there is a major tide expected -- can be up to 3-4' in extreme cases helped by the moon and wind
-- we've found ourselves sitting on the bottom (luckily in mud) in Factory Bay (Marco Island). No problem, just wait for the tide to rise and away we went.
Secondly - depending on where you want to be on the SW FL coast, you will still have occasional freezing to sub-freezing temps some nights. We moved from Burnt Store Marina (Punta Gorda) to Stock Island Marina (Key West) last winter to get away from the chilly nights. The Keys is generally 10 degrees warmer at night, although similar during the days, over the winter.
Charleston is nice too, but I'd guess it's chillier there than Charlotte Harbor
(Burnt Store) or the Keys.
It's a nice sail, come on down!