Miami / FT Lauderdale is not a good area to buy rep watches because law enforcement has pursued dealers very aggressively. They even created a counterfeit task force at one time, which was very active. Owning or buying one or two reps is not illegal, but selling them is. Buying with the intent to sell or in quantities valued at more than $1000 is also illegal.
Rep watches have not been popular in Miami, but rep designer handbags, sunglasses and women's clothing are sold by individuals all the time. Again, not from stores; the sellers usually know the buyers or are referred to others by known customers, mostly women. Oddly enough, genuine and fake Cuban cigars, both of which are illegal, have resulted in more arrests than rep watches. Selling Cuban cigars even got one Miami cop arrested and fired.
I've seen people selling rep watches, but these are individuals selling one on one to people they know. Again, most of the times is women who usually sell handbags and clothing that offer rep watches for their customers' husbands. There are no shopping areas like in NYC or LA where merchants offer reps for sale to just about anyone walking by.
Miami is good if you're looking for good prices on gen watches. The Seybold Building and many other jewelry stores in downtown Miami are great places to purchase gens at very good prices. Bargain a bit from the first quoted price because dealers are very slow now and they are motivated to sell.