Thanks for the tips!
Thanks so much for the very helpful suggestions. I'm particularly glad that someone has experience with the Mariner Sailing School - as I'm in DC it is much closer than Annapolis, and seems to offer a very good value. (My one concern was that there might not be enough wind on the Potomac to learn properly.)
I had looked into the Annapolis Sailing School, but had crossed it off the list because I found a comment (yelp? here?) that they didn't refund or reschedule classes if there was bad weather.
I will also look into a community sailing program. I found one here, but the marina looked to be highly unpleasant (very urban, have to motor around cruise ships). I hadn't thought to extend that search to Annapolis.