made a few nice discoveries on my recent trip to Oaxaca that I thought I'd share.
1. Tlayudas Libres. It's a tlayuda stand that pops up on Libres, just above Morelos every night at about 8:30-9 pm. They cook them right in the fire so they're nice and smoky. Cheese and a thin black bean paste inside, your choice of grilled meat on top. You can sit out by the cart, or at tables inside, or in the parking lot in the back.
2. The tamale lady. We were tipped off to her by a co-student in Iliana de vega's cooking class. Tried only one of her tamales on the way to dinner--a salsa verde one--it was tremendous. She sets up shop at about 7:30pm, and stays there until her food runs out (usually takes an hour I understand). She is in front of the farmacia on the street that radiates off the zocalo from the corner where Casa di la Abuela is--one block west of the zocalo (speaking of which, their food is pretty mediocre. I had some hideous chiles rellenos there).
Enjoy Oaxaca City; I did!