I live in San Antonio, so we have the heat and humidity here too, but my family is fond of fillings that have to be refrigerated, so last summer I tried putting my daughter's birthday cake in the fridge. I figured if it didn't work well, at least it was our cake and not going to someone else. It did fine. It was refrigerated overnight and then I took it out about an hour before the party started. It looked perfect, never developed condensation or any other issues. We didn't have a very good air conditioner in that apartment.
I've refrigerated all my cakes since then and had no problems, either in that apartment with the bad air conditioner, or in my new house where the air conditioner works really well, and they've all done fine. My mom sometimes wants a cake for her freezer, and she'll thaw it out and serve it a couple months later, and even those don't have any problems.
The only time I've ever seen condensation on a cake was when I froze squares to cover as mini cakes. They developed condensation as they thawed, and it evaporated within an hour, leaving the fondant looking perfect.
It may depend on recipes too, I use MMF and Indydebi's buttercream.