Lots of places in DuPont circle area. There is a large Mexican place that is great and a small pizza place that is to die for. I'll get u names when I remember - but yelp DuPont circle area. The Diner (that's the name) in Adams Morgan is great for breakfast.
I'd say that the extended loop Hop-on / Hop Off bus will give you a terrific feel for the city overall, then decide. That being said, the Museum of the Native American has the best cafeteria by far.
