Reid,
What are you flying now?
Almost any R/C plane that's not marginally stable to begin with will work on floats. If you're budget limited (who's not?) then just slap a set of floats on the plane you are already flying. If you're even slightly clever, you can make the floats and wheels interchange so you can fly wherever. When you add the floats, check the balance. Adjust the weight of the floats to bring the balance point back where it should be with wheels. So, when you replace the wheels, the plane will still be balanced for that, too.

BTW: the seniorita is not hard to build. Gluing sticks is pretty easy. THe LT-40 ARF is essentially a seniorita preassembled for you.

Jim