I believe that Kaz Sushi Bistro is on I Street between 19th and 20th.
Another idea for a Japanese lunch is Sushi Taro 1503 17th Street (P Street is the cross, I think)

Minibar is lots of fun. I went there last week for the first time, but I believe it is closed on Sunday and Monday.

Other suggestions: Equinox-right by the White House. Hotel Washington on the terrace - Best View in DC but mediocre food. There is a non-terrace restaurant that is located on the top floor as well. Although the view is lacking you might be able to convince them to serve you the better "indoor" food while sitting on the terrace. Woo Lae Oak Decent Korean restaurant in Pentagon City. Lebanese Taverna in Woodly Park. Red Sage - south western food in a fun (upstairs) environment or fancier food in the lower level dining room. All of the above are metro accessable. So when are we going??