I'll second the Arturo's suggestion above.
Faced with the same choice, Arturo's vs. Lazo's when we moved to the neighborhood, we chose the Arturo's. At the time it was more run-down on the outside and busier inside -- which from my east coast diner past are two signs of a good local eatery when they occur in conjunction. Local license plates in the parking lot is another good sign, but that doesn't apply here. (although cops eat here and that also is a good sign.)
Our usual fare is burritos, tacos, sopes and especially the chile rellenos.
We usually get pork, steak or al pastor.
I agree the chicken can be dry, but other times it seems to have been warming in some wonderful juicy sauce and is quite good.
Note: You can ask for carnitas on a taco or sope even if they don't list it (yum crunchy bits of skin and juicy pork).
The prices have gone up a dollar or so in the past year -- no longer 4.95 or 5.25 for a burrito but it ain't gonna break your wallet either.
Irazu is also very good (and yes not mexican but similar) and these places are both easy walking from the Western Blue line stop.
We tried IXCAPUZALCO at its new La Bonita location a few months back and would GLADLY trade in that meal for 10 meals at Arturos.
The goat cheese chile rellenos at IXCA were filled with carrots, the lamb chops had maybe two bites of meat on them. The moles were salty, soulless creations. The salmon portion was tiny. The chips and margaritas weren't even up to par. Very sad. We were excited to hear they had moved so close to us. Ah well.
(We have also had poor experiences with Frontera as of late and have moved to Chilpancingo as our destination when out of town foodies request Frontera.) We also tried Adobo Grill on Division with a coupon and know that if we had paid full price I would have felt dissappointed (overpriced, small portions, a couple good appetizers but in the end not worth returning for).