When I arrived in Mexico City in 1990, there were perhaps two or three places in the centro where you could find a good espresso. Most of the rest of the city was a wasteland. What they called coffee was brown dishwater, and most chilangos seemed to subscribe to the belief that things go better with Coke. All that has changed. Now the city is crawling with cafes, including hundreds of Starbucks, as well as their Mexican competitors Cielito Querido Café and Café Punto del Cielo.
My favorites are still the old ones. If you find yourself in the vicinity of the corner of Luis Moya and Manuel Marquez in the centro -- down the street from the San Juan Market -- and you want a coffee, don't miss this little gem of a cafe called Picolina.
It's very old school, with somber, serious waiters. They have a huge menu of special coffees with things like condensed milk and honey, which are not my thing, but their espressos and americanos are terrific.
Snacks are also available.