A michelada is a beer (of whatever type) with chili and salt on the rim and lime and chiles and peppers (a sort of salsa) in the bottom. El Importador, one of the open-air restaurants on the zocalo, has a fantastically cold and spicy version.
They also have a selection of regional fare, including the Oaxacan tamales I tried on Wednesday night. Wrapped in banana leaves, the dish consists of two large tamales and nothing more beyond an essential salsa.
The tamales are surprisingly sweet although they are filled with meat (chicken) and beans (damn the epazote). Several spoons full of the salsa make the dish even better. But it sort of feels like throwing ketchup on top of something to try to make it more palatable.
Fortunately, the rain drove a half dozen or so street children to my table to play with my phone; they finished any leftovers in a flash and wanted me to order some more.
I say go to El Importador for the friendly service and other people on the street; have a michelada and botanas (snacks). Skip the entrees, and enjoy the night air.