I was walking my dog this afternoon, and the window at M+J Restaurant (883 Franklin, a few blocks below Eastern Parkway) caught my eye: pics of tortas and tacos.
I walked inside and talked to the owner. She just took over the place a couple weeks ago, and she's slowly transforming it from catch-all Spanish eats to rustic, authentic Pueblan-style Mexican food. I tried a couple two-bucks tacos and they were tasty times. It's only going to get better as the menu changes are implemented. She mentioned wanting to add beer and wine, too. A good sign.
Given the epic lines at Chavela's, this may one day be a nice affordable alternative.