In Florida I'd have to go with Orlando. Orlando is on the right track and has room to grow. The only problem with Orlando is it's economy being based on tourism so there are a lot of unskilled low pay jobs.
Miami will probably continue to grow and just get bigger and bigger as the years pass but it's already well established.
Tampa, I don't really expect to see a lot of growth here. The epicenter for business is New Tampa rather than downtown. The city already has sprawl galore and a lot of traffic. I just don't see it growing a whole lot in the near future.
St. Pete, this city is more or less maxed out as it is. It will probably start to grow up more once the real estate market improves.
Jax, tons of room to grow but I don't know whether or not it will.