Hope we have some good wind over the time you are here. For open ocean conditions Mike described some locations near the Breakers. A bit further north is Jupiter (actually Juno) and about 45 minutes north of the Ft. Pierce Inlet. The nearest flat water is in Biscayne Bay. There are some good sea taxi operations that will take you offshore to these spots south of Key Biscayne in Miami. More at the first two posts at:
http://fksa.org/forumdisplay.php?f=42