The Round Treasure Island Regatta is this weekend, July 6-7, starting at the Encinal Boat Ramp in Alameda. Come visit in the morning around 9:00 AM and start bugging us. We shove off around 11:30 and return around 3:30-4:00. Go here for dates and locations of this season's regattas:
http://hcana.hobieclass.com/events/Hobie Fleet 20 (
http://www.hobiefleet20.com/index.htm and Facebook) has monthly fun sails at either Lake Camanche or Woodward Reservoir until October (we just had one this last weekend) and if you make your desires well known in advance then arrangements can be made to get you on a boat.
There is not an active fleet sailing regularly on SF Bay.