I am in Texas not Florida but do some web searching before you go as there should be alot of shops. Some will depend upon brand you are looking for. Use manufacturers websites to give dealer names in Florida then check their respective sites.
As for coming back.
I usually have to check my guitars (all dependant on flight/carrier/crew etc.) but if ya bank on putting it in the hold then anything else is GRAVY! Therefore a hardcase is a MUST!
Also, if ya can, scuff the case abit or buy used. I have not once been stopped by Customs in UK (not that it would do em any good as am UK Citizen and US resident but still).
I too am not a Guitar Center fan, or any big chain ala Sam Ash, but doubtless they are worth a look as are very big and good to browse.
Alot depends on what you are looking for. GC carries some main brands (alot dependant on location as some have Bogner/Diezel etc.) like Schecter,Fender,Gibson,Jackson etc. But many have been handled by countless 13yo snotty Greenday humping teens with ginormous belt buckles and such aka are fecked!
Any specific info. post/pm and will try and help a little if can.