Some girls/agencies are discovering Old Town, Alexandria (and I think its great), the problem is limited clientele. Albeit very wealthy clientele in the area. One hotel is easy access, but average. The other two are nicer, but not easy to get to the room without walking directly in front of the reception desk. One of those two, they don't care because its too busy, but the other is pretty obvious why you or your client is there and what purpose.
The limited client base in Old Town is because you have a river on one side, thin residential area (relatively speaking) because of airport to the North, Parkway/Park to the South, and military base chewing up the rest further North.
That being said, girls tour there periodically and seem to pick-up a niche market starved for the right provider. An agency I know of sends a girl there about once or twice a month, but that is it.
Crystal City would be better, but I don't understand why more girls don't tour there, may be a limited clientele base of government workers and a lot of companies have moved out of the area for Tysons or DC. Also, parking is a bitch and a quick in and out by metro difficult because a big of a walk for most hotels.