I want to have a cake/sweet stall but as i live in Miami where it is very hot I'm afraid everything will melt. What would you suggest I bake that will be fine in the heat?

Why not try selling baked goods that are traditional to countries with a warmer climate? Or simply baked goods that don't need to remail cool or moist. Here's a few suggestions:

Baklava (Middle Eastern)

Banana Fritters (West Africa and Caribbean)

Frappe (Italy)

Jalebi (India)

Churros (Mexico)

Ok I'm going to go grab a bite to eat now, good luck!