Some of the best, most authentic tacos (I should know because I'm from California, right?) can be found in a back window inside a tiny Mexican grocery store on 10th Ave (between 47th & 48th Sts) in Hell's Kitchen. I don't think I would have ever found it if one of my neighbors hadn't told me about it when I live around the corner for two years. If you can find it, give it a try. It is, literally, a hole in the wall. Super cheap ($2/taco), super delicious (most people love the pork, but my fav is the chicken). Tehuitzingo Deli & Grocery.