Here in DC, I have Nando's occasionally, and there's a Pret-a-Manger downstairs from the office. Vapiano also has at least a couple of outlets (also one in Mexico City), but I've never been. Mexico City has all the usual US fast foods. There are Sushi Itto outlets everywhere too - I'm not sure if it's a Mexican company or not though.

I'd really like to have a Frankie's of Bombay cart downstairs - those things are delicious.