You will likely do much better with places already mentioned, but I'd still recommend to come here (or forums like CruisersForum) if you need more specific answers. This sub has some folk who are pretty solid, but the deep knowledge is often in forums.

Sail trim, reading water, etc is indeed best done in person, and you should find many capable people there (particularly in the racing crowd). See if you can find people familiar with the local currents and eddies, the current flow is not a simple "either ebbing or flooding"; there is often still water coming in even when the tide is ebbing, and similarly the height of tide is not exactly aligned with the ebb and flood. Largely this matters for racing, but it can help anytime you might want to make better progress.

You'll also want to factor the current into decisions like "when do I tack?" Otherwise, you'll tack too early and end up having to tack back and forth later. Don't worry, you'll eventually get a feel for it. You'll just learn faster once you know to watch for it!

As for "seamanship", exposure to a number of people and boats will help you identify what's good practice or not. A good general rule is to prep early and keep things tidy, because a task left for later has a high risk of becoming a blocker once something else becomes suddenly urgent.

What I'd particularly double-check is weather, navigation, and rules of the road. If you do racing you'll have a separate set to learn, with plenty of opportunity for rules-gaming. (Or so I'm told; I'm not really a racer.) Read the rules yourself; most people and texts will simplify them and get aspects wrong (often because they skip the definitions and don't realize certain phrases have particular meaning). For weather, always look a few days beyond your planned trip: often a "wrong" forecast is simply a case of the weather arriving earlier or later than expected.

Some other thoughts/resources:

• South Beach is a convenient location and there's a small school there as well (Spinnaker Sailing, which might be the same name as one in RWC so double-check).
• Modern Sailing, since the demise of Club Nautique,^1 is one of the better schools if doing lessons. Their bases are Berkeley and Sausalito.
• Cal Sailing is best on a budget, and probably for learning precise control like docking under sail, and they are based in Berkeley.
• If racing is your thing you should find plenty of opportunities. If it turns out to not be your thing, don't let that put you off sailing (avoid boats with skippers that yell).

Ah... Ok, I think that's enough typing for now.

^1 There are efforts to resurrect this in the form of Group Nautique, thus retaining some of the boats, instructors, and community. One of the key reasons I'm interested is that it would be one of the few options to charter boats and go up and down the coast. Two other ex-CN boat owners have formed Pacific Wayfinder Sailing Academy out of Alameda with ex-CN instructors; ideally both will be doing classes over the summer and expanding offerings over the coming years.