Hello Roy, yes for now you can ride at South Beach. I would suggest avoiding crowds of people and getting beyond 100 m as quickly as possible and staying beyond that distance until it is time to come in. Sobe is crowded so if you are still learning to stay upwind, I would suggest that you hit some of the less populated beaches further north near Bakers Haulover Inlet or even in Broward County, north of Dade (the county that contains Miami). Alternatively, you could do assisted launches and landings in the shallows off much of the Florida Keys to the south, in nice calm, often fast conditions.
Have a good trip,