Ive never been to a Florida MLB game, the closest team is in Tampa. Ive been to a Brave's game, which since they were doing well at the time might not be a very good reference, and it was packed.
That seems to be in support of your thoughts, and I agree. Ive been to a few NFL games outside of Jacksonville, and they are pretty much always full. Albeit the games ive been to have been Steelers games...more notorious fans.