There is an unassuming sea-side stand near the town of San Blas on Playa Hermosa, just north of Puerto Vallarta, that has the best Mexican food I've ever had. Fish tacos, burritos, enchilada's and very cold beer. All for $1US each. Spent 11 days there hanging out in a hammock on the beach during my motorcycle ride from San Diego to Buenos Aires. I almost married the cook's daughter. Such a dark-skinned beauty ... with eyes like emerald pools .... long, straight black hair ... brilliant smile ... oh, sorry.
We had Mexican last night at Mole on Cabildo 1400 (mas o menos) in Belgrano. Tried it 4 years ago and it was horrible. Last night was pretty good. However the "spicey" Mole Chicken that they had rated at "3 Peppers" didn't really hit the hot scale. You need to ask for their "special" hot sauce if you want anything with zing.
I have been routinely disappointed with Mexican food in Buenos Aires. For Ameri/Mex you can try California Burrito Company in el centro. Maybe it's on Lavallle?
Food trucks are illegal in BA, notwithstanding chori trucks which are mafia-run/their own mafia (I'm not sure what the actual details of it are). Fun stuff, eh? Evidently the law prohibits anything that produces smoke in the streets.
As for Mexican, I haven't been there for a while but I used to love the fajitas at Maria Felix (the one on Godoy Cruz and Costa Rica I think, in Palermo, there are several places though). They even started carrying corn tortillas the last few times I was there. The vegetable fajitas come with tons of different vegetable selections, you get free chips and salsa, several hot sauces, it's great. The meat selections are pretty good time, even though they might not be super authentic spice-wise, but tasty nonetheless. They have a burrito on the menu, but I don't think we've ever ordered it... maybe once, and I think it was big and delicious...
I haven't been back in so long I guess because I've been going to the states so often the last couple of years that I have been getting my Mexican food fix regularly enough. Someone please go and let us know how it is these days! Oh, they also have a mariachi band sometimes, which is actually a pretty good one!!
Tez, MF is fine but it's not authentic Mexican by any stretch. I call it Argentine-Mexican. Basically it's all pretty bland. (And we go there fairly frequently but I know what I'm getting into to when I go.)
I have yet to find any truly good Mexican and/or Tex Mex here. I enjoy Lupita and MF and the others but again, not authentic in my opinion although not bad in their own right.
I make my own when I have mexican cravings now - it's better and easier. I stock up on spices and supplies when I'm in the US. Just made fajitas last night in fact. Although I do cop to using flour tortillas now - I can't find corn out by where I live and I have yet to try making my own.