Jay's Saloon in Clarendon (just a couple of stops up on the metro in Arlington) is probably the best dive bar in the area - from the Key Bridge, take the metro up to Clarendon & walk up Wilson Blvd towards the Hess gas station & make a left on Fairfax (maybe called 10th street too) & Jay's is about 2 blocks up on the left, right past the Avis sign & near a small unbranded car dealership. After drinking, you can grab a slice of pizza late night at Mario's Pizza House (right up from the Hess station on Wilson - best pizza in town! - they're open til 4AM).

Also, there's a good dive bar in Ballston - but I can't remember the name of it as its been a while since I've been there - it's on Fairfax as well & sort of next to the 7-11 & the Food Factory Indian restaurant - it's got a yellow sign.

http://www.washingtonpost.com/ac2/wp...file&id=795123 - Jay's Saloon

If you're staying at the Key Bridge, there's not really much in Georgetown or Rosalyn, unfortunately. Cowboy Cafe is also nearby, but I don't think it's metro accessible & you'd have to cab it both ways from Key Bridge (unless you have a car - and if you plan on drinking & driving, it's a pretty straight shot down Rt. 29 to get back, but there are often cops on that road). Here's a review of Cowboy Cafe - http://www.washingtonpost.com/wp-dyn...0601817_4.html (if you read the whole article, it'll mention Dr. Dremo's in Arlington, that place has sadly closed down).