I've been in touch with the Santa Clara County Vector Control folks, and they said to contact the members of the Santa Clara Bee Keepers Guild (www.beeguild.org). So I've left a couple of messages on members' phones, in the hope that one of them would be interested in coming over and rescuing my swarm. Hubby says I should call Terminix and get them "removed" (aka destroyed), but that's only because he has a deep seated loathing of bees that originated from being stung many times as a child (when, to be fair, he had apparently covered himself in jam, so he was asking for it). Given the fragile state of the world's bee population right now, I'm not going to do that.
Here's a pretty interesting article with photos on bee swarms. Sounds like we only have a small one. http://www.beemaster.com/site/honeybee/swarms.html