We had lunch under the umbrellas less than one block from the White House on a beautiful September day. It was a business lunch but that didn't stop us from enjoying the location and the weather. The restaurant is part of the Willard Hotel on Pennsylvania Avenue. I will say that the street in front of the restaurant is Very busy and filled with traffic so don't expect serene here but the view of the Treasury building is good and the people watching is great. I also would not recommend it on a summer day since Washington can be oppressive in the summer--they do have a very nice indoor dining room though if it is hot.
We all had sandwiches. Mine was grilled chicken with avocado, arugula, tomato and dressing on a very nice roll. It tasted great but it was a bit juicy so I cut it with a knife and fork to avoid spilling it all over myself. It came with very good French fries. My colleagues had a lobster roll and a pork sandwich, which both finished to the last drop. We didn't have dessert but we did have cappuccino which was lukewarm so I can't recommend it.
Our waiter was excellent and attentive. We had to wait for nothing.
The prices are a bit high but you can count on excellent food and good service in a prime location.