We got down there about nine for the first 'official' presentation. Many hundreds of people there when we arrived - many hundreds more by the time we left.
Looks to me like the best way to get there from anywhere very far away is to get off BART at the 12th Street station - you come up in the middle of the crowd. [Until they close that station, of course...]
A few pictures below the fold/Kos croissant.