Up in Ft Lauderdale you will have a small sailing club in John U Lloyed state park that rents a few hobie waves I beleive. To get there from Ft Lauderdale, get on I-95 south, get off Sheridan street. All the way at the end of Sheridan, and I mean the END! just follow the round about, and it will take you into the park. just ask at the gate. It is a dollar a person to get into the park.
OR you have
Key Biscayne there is a spot just south of the Rickenbacher Causeway, it will be on your right hand side when comming from Miami. I would go here, nothing better than sailing Biscayne Bay, plus there is a much bigger selection of cats to choose from.
To get there from Ft Lauderdale, get on I-95 South, just after you pass downtown Miami get off the Key Biscayne exit, onto Rickenbacher Causeway, the exit will be on your right hand side. Just follow the signs you can not miss it. It is a one dollar toll fee to get across the causeway.
Good luck and have fun!!!