This is where you want to be. Just far enough away from Dupont Circle to be quiet, but close enough to get wherever you want to be in the district with no hassles. The neighborhood is gorgeous and calm, and if you're a real nerd and like to play the game "guess that embassy!" by identifying their nation's flag - just walk out the door and head in any direction.
The space itself is incredible. It's an old building, but modern where it counts. It was just the two of us this trip, but you could do four easily and not feel cramped. We didn't cook while we were there, but the kitchen is fully stocked with what you might need for making breakfast/dinner (bonus - the neighborhood Safeway is about a five-minute walk away).
Two other things to remember: this is a third-floor walkup, so think about that if you're packing 70lb+ worth of baggage. Second: this is an old building, so make sure to pack your favorite pair of fluffy socks/slippers for wandering around the house - you're going to have neighbors beneath you, so the no-shoes thing in the apartment is a good rule.
Enjoy!