There are many sailing schools around SF, but one that stands out is https://www.cal-sailing.org/ - as it's by far the least expensive and low-commitment option to get on the water, and they have dinghies in which you'll learn very fast (but also get wet). Instructors are regular volunteer club members and mileage may vary, so make sure to go out with a few different ones.

Another good way to get started is to find crewing opportunities for casual racing on https://www.latitude38.com/crew-list-home/. Many skippers will take no-experience folks out for fun. (It may take a couple of attempts to find a skipper/crew you enjoy hanging out with)

I found CSC friendly but basically the boating equivalent of opening the encyclopedia at random and reading -- whichever instructor I ended up with would just decide what he wanted to teach/do that day, no structured curriculum. Presumably one could eventually learn enough to pass the test and be able to take dinghies out yourself, but I didn't have the patience--I bought my own and learned more in 30 minutes than I ever did at CSC

If you want to learn how to sail and actually how to sail as the person in charge, you need to be in a dinghy. Its small enough that every thing you do will affect the course and speed, you can feel every little difference and nobody else will confuse the issue by moving or changing anything without you noticing. Sure, having instructors around giving you tips is necessary but you are doing it and the feedback is immediate.