83 Mount Auburn St
Cambridge, MA 02138
http://www.felipestaqueria.com/
I checked out Felipe's Taqueria mostly based on the amazinf smells coming out. Felipe's is a taco / burrito assembly line, with a Mt. Auburn Street entrance and Garage mall entrance. I was glad to see a lot vegetarian options, not just a half-hearted salad, but I wasn't feeling it today, and tried the pollo tinga tacos.
Prices were pretty inexpensive (Well, for Boston, that is. About the same as table-service Casa Margarita and Los Tres Magueyes in North Carolina. But, hey, I'll pay a LOT more to finally be in a place that doesn't overlook a parking lot.), ingredients tasted fresh, and everything's put together in front of you, so the chicken is hot and the tomatoes are cold.
There's also an amazing fixings bar. My standard for awesome, flavorful salsa is the salsa bar at La Veracruzana in Amherst. Veracruzana's salsa bar includes killer Salsa Diablo and a fresh tomatillo salsa. I've often gone for Mexican food in other places, looked over at the Boy, and told him how much better things would be with Vereacruzana salsa.
But Felipe's put them to shame. Classic salsa, tomatilla salsa, radishes, jalapenos, lime wedges... anything you could think up to make your tacos even more delicious.
It was extremely crowded when I went in, but the line moved pretty fast. When I got to the front, I realized this was because the servers were efficient, even if they communicated mostly in grunts, and seemed to get annoyed when customers wanted to slow their progress by asking about the ingredients. Don't be deterred by a lack of seating, the Newton Market green is just across the street, and it's a perfect spot to eat and peoplewatch.