Google for a couple previous posts on this place.
We got takeout, but while waiting I noted that the place, although small, is extremely clean and comfortable. I'd definitely eat there next time.
We got the tacos especiales, which is 4 tacos with a meat of your choice. We tried 4 different meats.
*Al pastor was of the saucy chunk variety (not sliced from a big rotating gyro thing) and was sweet and savory with a pleasant texture.
*Cabeza (beef cheek) had all the best textural characteristics of fattiness and dryness at the same time, with a rich beefy flavor.
*Pollo was a great surprise, with stringy and moist chicken appearing in large pieces that ran the length of the taco, not tiny little chunks.
*Carnitas had a nice, porky flavor but were a bit dry.
Each taco had a generous quantity of meat and came topped with a couple thin slices of avocado. Tortillas were fine but nothing special.
We also had the plato mexicano, which included:
*Competent refried beans
*A "beef" taco overstuffed with totally flavorless, chewy bits of meat... don't get this one
*A very dry chicken enchilada
*A slightly moister enchilada of ground beef. Good flavor but still not saucy enough.
I'd recommend avoiding the plates with rice... I really didn't care for it. Definitely avoid the "beef" filling.
Overall, the quality of the slow-cooked meats was very good. I'd say that the food generally suffered from a lack of acidity. Our to-go bag was packed with several containers of a homemade hot sauce, but the hot sauce was very heavy on smoky, dry chile flavor and totally lacking in acidic bite. I ended up pulling out some of my own hot sauce to fix things, since I was without citrus at home. I'd imagine that if one eats at the restaurant, slices of lime are available.
Overall, I like this place a lot better than Taqueria Mexico (better spicing, much fresher and tastier meats, smaller but more comfortable atmosphere).
I've linked to Burrito Blog's page on El Mariachi, which includes a link to the menu.
Taqueria El Mariachi
196 Willow Street (just off River St near Shaw's)
Open until 10 but closed Tuesdays