I'd look up local historical societies. The art museums do sometimes buy up entire collection or take donations;
but they mainly acquire from serious private collections selectively at best. Funds and archiving space, and personnel, are quite limited; and many museums these days are seriously underfunded; and any Fed backup is either about to get killed, or already has been. The Oakland museum has the best historical archives, but is already stuffed to the gills in terms of a massive photo collection.
Most people I know are mostly interested in pre-1906 documentation. But SF is otherwise a good city with respect to its own historical interests. It might take some patience, but some kind of party out there will probably be interested. Galleries want catchy things either they can sell, or which in their opinion has social relevance. It would be pretty hard to interest one of them, and display slots can take years in advance to assign. Some kind of local neighborhood association venue in a library or bank might be possible, or perhaps some restaurant or realtor group.