We hit Keys Cable last time we were down, they have 2 system 2.0's....one with features and one for beginners. They have their own private 7 acre lake for it, always good water.
You can also charter a Whaler for wakeboarding on Islamorada. Same place that rents jet skis. (Jet skis are fun to explore around there too!)
I don't think anyone rents wakeboard boats in the Keys, I looked.
I was njskier on here.