Yeah, there’s a couple board game cafes in Toronto with bulletin boards for people looking to meet other game enthusiasts, there’s probably at least one in the Bay Area and it would be a good place to look for LEGO buddies
Legoland discovery centres also have adult events on a periodic basis. Normally you’ll get turned away if you show up there without a kid though, so be sure you confirm ahead of time that you’ll get in
now I need to afford relocating to San Francisco...
Or put up fliers at the library?