I dared a friend to find me vegan Mexican out by my mom's (Mt. Diablo) and he found this place in Concord: Memo's. www.memoscuisine.com/menu.html
They are incredible. There's a cute/shaded cactus garden outside, super cute Frieda-Kahlo decor inside, everything is local/organic and run by a father-daughter team. The daughter is vegan and is so excited to have other vegans come in. This place has the Mexican food of my dreams. It's incredible. I wish I weren't going back to Europe tomorrow so I could eat there again and again. I can't recommend enough -- you guys should have a meet up there and go!