If you want to be able to ride or take metro to work, I think your best options are in VA. As you've no doubt seen from a metro map, you want to be on the orange line. The route that the orange line takes through DC is mostly thru downtown - more business areas, a bit less residential. (Not that you literally can't find a decent apartment in DC near the orange line, but you have fewer options than, e.g., if you were looking along the red line.) Depending on how much you have to spend, you might be able to find a place right in Clarendon or Rosslyn. Ballston is also a good option. Any of these would put you close to work and to good places to ride.