Doomies (instagram.com/doomies/) in LA for vegan junk food including an awesome Big Mac as a "secret menu" item, had great fried "chicken" bits there too, we went back the next day..
In SF there's plenty of street food places, No No burgers were stand out: instagram.com/nonoburger/
Also in SF there's a great Mexican place in Mission called La Taquiera, I'm vegetarian but I'm sure you could go vegan there too. The place was busy but amazing, well worth a visit. m.facebook.com/LaTaqSF/