No laws regulate the usage of SE in Florida so it is pretty much meaningless to call yourself one there. I would suggest getting a license in a state such as Illinois that does regulate the SE title so there is no grey area in calling yourself a SE.
I am currently a PE in Florida, but an SE in a few other states. My signature typically reads "PE, SE". Though I think I might add in a line about what states I'm actually licensed in to ensure that I'm not violating any rules.
