I attended three universities (for three different degrees) and am an alumni mentor for students at all of them. The one thing I consistently stress to students is that at the age of 18, whatever you think you'll be doing in 10 years, I can pretty much guarantee you that will be doing something else. My point, to them and to you, is that it's not worth stressing about issues that you will only need to make decisions about later in life--such as where you want to live/work AFTER college--when you haven't even started college. It's also a good idea not to lock yourself into a life goal at the age of 18, if for no other reason than when you discover at some point that you actually don't want to achieve that goal, you won't incur any psychic damage from ditching it. (I learned this one from my own experience; from age 12-18, I was bound and determined to be an architect, but after starting school for it, decided it wasn't for me. I ended up, at age 30, in the investment management business, which was a much better fit and a wonderful career.)

Arlington is fine, but I prefer the District--much more character. I lived on Capitol Hill for a few years and found it a much more congenial place for a young person than the relatively stodgy NoVA. In any case, if you go to JMU or GMU you'll figure out pretty quickly what the best places to live are.