I've been obsessed with cheap Mexican food in the Hayward / Castro Valley area. Two new ones (for me, at least):
Tacos Gullense (sp?) at B Street in Hayward right below Val's Hamburgers (the Papa Burger at Val's is too die for, BTW) in the old Taco Bell location & building: I sampled the chile verde sope and a chicken taco. Both meats, very flavorful and came with different salsas, but you had to know to ask for a salsa verde. I don't believe either the sope or the taco had homemade tortillas. Jalapenos and radishes served on the side. Taco: 1.00; Sope: 1:50. Pozole on the weekends with homemade torillas, though.
Taco truck (called Taco with a last name beginning with a "G") parked at lunch time in the 76 gas station at Grove and Center, in front of the liquor store. I had the carnitas and chicken tacos. 1.25. Carnitas just the way I like them: crispy at the end and tender toward the middle. Chicken o'k. Came with lemons, and a pickled carrot and jalapeno side with fresh radishes. Very good. And clean. Not handmade toritllas.