Ummm ... Bonney Field in Sacramento is a soccer stadium in Cal Expo - capacity 11K, poor access/egress. IOW, it's not AT&T Park, the LA Coliseum, or the Rose Bowl in terms of capacity, and Cal Expo is designed to be the site of the state fair, not for efficient access and egress of large crowds. So the DU folk, in their ignorance, are mountainizing a moderate-sized hill.
That said, The Bern is mounting an earnest campaign in CA. He's not just sticking to the neighborhoods of SFO, LAX, and SAN. Today he demonstrated his solidarity with the working folk of the Stockton area by holding a 7AM rally in a venue near the junction of I-5 and SR-4 (a significant freeway interchange). I'm sure all those Central Valley workers whose daily commute was made extra wretched are completely motivated to vote for The Bern!