30 miles in this area would not guarantee you a 1 hour commute, especially if you live outside the beltway and are coming in. I live inside the beltway and drive to DC, I leave the house at 6:50 and still hit some traffic making my 11 mile commute in 30 - 40 minutes, if I leave the house later at say 7:15 it's 45 minutes min, and when I've had a dr appt and left at 9:00 it takes over an hour.
Chris suggested Fairlington in Arlington, they are older townhouses, but usually fairly reasonable for Arlington, it's not near a metro. However, depending on which part of George Mason your office is, it may not be near a metro either.
If you can get inside the beltway you'll be happier. I'm on the Annandale line and it's more affordable here then Arlington and still inside.
Our traffic is bad on a normal day, if it rains things come to a standstill. So you want to get as close in as you can afford