Oh boy... that's like asking where the best Eskimo food in Alaska is.... :think:
We eat at Taco's Brisa quite a bit - it's on Sinaloa about 3 or 4 stop signs north of Fremont, and we've never seen them jack up prices or anything. Their salsa is spicy, and they always throw in some grilled jalapenos or green chiles with your order, but the chow is first-rate.
Back in the my wild days, BC (before children) my college buds and I would drive around on what we called "taco quests" - we would find a taco spot, order one taco, and each of us would take a bite, and if the place was good we'd sit down and order 20 more and stuff our faces... if the taco did not pass muster, then we'd move on to the next stop in search of the ideal taco candidate.
If you want to enjoy tacos the way the locals eat, then you have to get off the beaten path a little bit. Sometimes, a converted ice cream cart with a hibachi on top of it becomes the source of some of the best tacos you've ever tasted...