This marketplace, which is quite traditional by most standards, is renown because of its food…read morestalls, particularly the seafood ones. While I amply -very, very amply- recommend those (La Fuente de la Juventud jumps to mind), there's plenty more to choose from, like Japanese food, Argentinian meat cuts, desserts and even a couple of gourmet options.
Even the quesadillas (which may or not include cheese, as is the custom in Mexico City and never fails to annoy people from other states) that place themselves outside the marketplace on weekends are on the very tasty side of the scale.
If you are around, it's always a good option. Parking may be tricky, but there always seems to be an army of "franeleros" ready to jump out at any corner of the city, so there's that. Or try in the streets around the place.