1) Hang out at marinas on weekends and talk to sailors. Lots of people will invite you. Especially racers. Hang out at yacht clubs for beer can races to get your first introductions. At our club we find a boat for everyone who wants to sail. Once you start sailing, if you pitch in for the work part you will find yourself more than welcome. Captains will start fighting over you.
2) Hang out at the start of the Baja Ha Ha and tell people you want to go sailing. If you are fit, presentable, polite, personable, hard-working, and have your gear ready, you are likely to find a spot. Parlay that.
3) Be self-sufficient and ready to live rough a little. Have a good sleeping bag and a small stove and pot in your gear so that if you end up camping under a bush for a few nights you won't freeze or starve. Have a good book.
4) Have skills. If you can fix diesels or refrigeration or fiberglass or can weld stainless or fix electronics or computers or do any of a hundred repair tasks, you make yourself more welcome.
: San Diego