Oakland Convention Center - quick lunch?
Caffe 817 is a great choice, but, although it ain't really expensive, it aint cheap either.
Cam Huong, on Webster between 9th and 10th Sts. is a good bet for a take-out bahn mi (French sandwich) - crisp outside soft inside French roll, pickled carrots, cukes, etc., and filling of curried chicken or beef and onions. You can acutally eat inside Cam Huong as there are a few tables at the back.