Q.Does Mel’s square foot gardening method do well in south Florida?
I’ve been able to obtain the #3 vermiculite, peat moss, and 4 compost (still looking for the fifth). I’d like to know how well does Mel’s mix do in south Florida. Also,how much water will the beds need?

Certified GKH Gardening Expert
It won't matter where you are, as that is usually a concern for the type of soil of your area. If you are mixing your own soil, then that cuts out the need to worry about your native soil, so yes, this method will work quite well, regardless of where you reside.
Now, as for watering... This is going to be something that you can't give an amount to. This will heavily depend on your area, the temperature and humidity, and many other factors.
The best way to determine if you need to water or not is to stick your finger down into the soil. If there is no moisture down to about two inches, then it is time to water. If it is still the least bit wet, then watering will be a bad idea.