The Coconut Grove Sailing Club has an excellent location in Coconut Grove, you would be able to keep your boat at a mooring or on land (depending on the size of the boat), it has excellent facilities, a great member community, and they are a US Sailing school. They currently offer Sunfish courses, a Basic Keelboat course (on a fleet of 23 foot Pearson Ensigns), a Basic Cruising course, and a Bareboat Cruising course. If you take the courses and the certifications, you could rent, for a relatively modest price any of the several Pearson Ensigns for daysailing, or a Beneteau First 265 for daysailing or cruising for several days...
They also host several regattas and have a committee designed to organize weekend trips to nearby locations such as Elliot Key, the Ragged Keys, Soldier Key, Key Largo, Rodriguez Key, and even Bimini and the Abacos!
I am a member myself, I highly recommend that you go check it out or visit their website at Coconut Grove Sailing Club