"Casual is good. Nothing too swanky please"
"Go get the beignet with foie gras, poulet, and a macaron. Round it out with a bottle of wine for the adults and drop a cool $700 on a casual meal for the family."
I love TexAgs.
But lots of other good recommendations on the list. Lots of mainstays like Old Ebbitt, Pete's, etc. I like Filomena but pricier and needs a reservation. I liked Pisco y Nazca as well.
If you're walking around DuPont circle or in the area of one of their other locations and want a cheap, quick snack while walking stop by Julia's Empanadas.
But really, due to the international influence and populations, there is a wide variety of food. Try something you normally wouldn't at home. Just try a local place and look up a few quick reviews to make sure it's above average before going in.