What is the average rate per hour for plumbing in the Miami, Florida area ?

I am not sure that you will get an answer to that question on here, why don't you call some plumbing shops in your area to find out for sure.

Rates for plumbing vary dramatically from area to area. I agree with letmetellu, your best bet would be to call some shops and ask them their hourly rate. Keep in mind, that if you are looking for a quote, the hourly rate is thrown out the window. Sometimes you win from an hourly rate, sometimes you lose.