I pretty much five-stared everything and I would definitely recommend staying at Duo Housing.
The staff over there were really nice and welcoming, the property and beds were clean and it's a great bargain. It's really cheap - much cheaper than the other locations available in DC - and it's so close to the National Mall, where you would find all of the main monuments, memorials and museums.
If you don't mind the shared bedroom part of the deal, go for it, you won't regret it!