There are a few hospitals in the Northern VA area that take LPN's but the majority of the LPN work is in nursing homes and assisted living. I work with Healthcare Works (agency) in the Tysons Corner area. They work with both nursing homes and hospitals. Let me know if you want their phone number.
I have heard good things about Loudoun, but since you are new to the area have you considered working for an agency so you can try out several different hospitals prior to making committing to one permanently. The Broadlands Hospital is also about to be built out in Loudoun somewhere.