The Reston Town Centre has some good happy hours and the women always hot. Clyde's, American Tap room, Market Street Grill. Tyson's has some nice places. If you want to meet nice women than look for a bar next to tall office buildings. THe real hot area around here for happy hours is the Claredon area. That's where most of hotties and young professionals go.
http://www.cgrill.com/
FYI - Bars are allow to set their own prices for drinks they offer. In Virginia a bar can have discounted drinks but can not advertise that.
Always ask your bartender or waiter if there are any specials.