Mexican Food, Boston Metro Area (A Huevo!)
Homeboy and I have exhausted the Mexican food establishments in the Providence area. We desperately want to fancy it up for our first year anniversary and the first year anniversary of his time in America.
So we want a sweet place to eat Mexican food. No taquerias, no BYOB, no "but it's so authentic that Don Fulano grinds his own pepita." We'd like a recommendation for a place that's fairly accessible by public transport so we can get sufficiently sauced. It's okay if they decide that they'll put cheese on the refried beans so that the gringos will like it, just as long as we can get there by train/T and have waiters who speak Spanish.
Don't wanna hear about an exquisitely seasoned mole poblano that tastes just like the viejitas en Oaxaca make, because he doesn't like that. A good carne asada, a b&tchin' margarita, and a short stumble to the T home will do us right.
So it sounds like you're asking for table service Mexican, not too fancy, liquor license a must, not totally phony.
Having grown up in the Southwest, our go-to Mexican spot in Boston is still our own kitchen, as nothing has been quite right, but here's a couple of ideas all the same. [Now it sounds like you and yours are a little excitable about your Mexican chow, so don't you be coming after me if these aren't your thing...]
La Verdad (Fenway) - can't promise they'll have Spanish speaking waiters, but they've got the location, vibe, and booze list you're after.
Zocalo (Brighton) - a few tics nicer than you may be after, but solid food and drink, right on the B line.
Border Cafe (Harvard Square) - I personally can't stand this place, but it's arguably the most in-line with your request. At least in vibe, it reminds me of home. Tex Mex through and through. It has a reputation for good margaritas, although they've never really won me over.
Zocalo Cocina Mexicana
1414 Commonwealth Ave, Brighton, MA 02135
1 Lansdowne St, Boston, MA 02215
32 Church St, Cambridge, MA 02138
Sol Azteca definitely fits the bill. Mostly Spanish-speaking staff, some mundane stuff but some outstanding exceptions (try their spicy sauteed chicken livers - higaditos Mexicanos - superb!). Full liquor license, with a selection of margaritas. They even have a nice outdoor patio. And it's easily T-accessible, take the C line outbound and get off at the first stop above ground, right after Kenmore.
GabachaYucateca, I like your style!
I, too, was going to suggest Forest Cafe. Doesn't look like much from the outside, but step inside and there is a sizable bar at which you will find a broad spectrum of people (Harvard law profs elbow-to-elbow with average Joes and well-known, hard-drinking Cantabrigian characters). I always eat at the bar - the food is decent and the pours are generous.
Tacqueria Mexico in Waltham fits all of your descriptions except maybe the margaritas (not sure if they make them, but they do have beer - Corona, Pacifico, Modelo). It is a sit down/table service place and but not fancy at all. Its just a few steps away from the Waltham stop on the Fitchburg commuter line. If they don't serve margies there, you could hit up Margaritas and/or Iquana Cantina (don't eat at these places) on Moody street for a couple of drinks, then head over to Tacqueria Mexico for some real food - all very walkable, just have to plan the trip to match up with the commuter rail schedule.
Outside the city, but right right next to a comuter rail stop is El Sarape in Weymouth Landing (actually located in Braintree). Sounds close to what you want. Great food (carne asada with chorizo and enchila plate...), great margaritas, spanish-speaking staff.
Taqueria la mexicana in Union Sq. Somerville (now that they have the full bar area) would probably be a good bet too...but this would be a bus or cab ride to the nearest T stop. actually, this place might be the better option is the goal is to get sauced...as it feels more like a bar with good food