There's a Lee's Sandwiches down the street (about a half mile from the courthouse) that I stop off at frequently on my way home from work. They have a pretty good selection of Vietnamese and American sandwiches, Vietnamese rolls, and things. Nothing fancy, but I've liked pretty much everything I've tried there. It's slightly more expensive than typical Vietnamese places, but they take credit cards.
24788 Amador Street Ste A@ Jackson St.
Hayward, CA 94545
Phone: (510) 783-6888
Fax: (408) 263-2688