dca is so close to washington that you could stay anywhere. And you will have a chance to do things in dc in those eight hours if you so desire. I too would recommend priceline, but you can look in dc itself as well as the airport area (which is called crystal city). There are number of areas open at night in dc where you could easily walk around including both georgetown and adams morgan. It's about an $18 cab ride or depending on where the hotel is, you can take the metro