I actually drove along the Eastern shore of Lake Okeechobee today on the way to the Steeplechase and it looks like it would be a great place to sail. Nice wind, miles of flat water, and no viable place to launch or stay.
I have never sailed there (or done anything besided drive by the town/lake) but they do have camping, lodging, and a
marina at Lake Okeechobee Outpost. there is boating / sailing / etc there..
PS i am not advocating it (not a fan of sailing with gators), i was simply answering the question.. "where is fresh water in SF"
http://lakeokeechobeeoutpost.com/marina.htm