I live right near Ballston and sometimes take 495 to 66 to get home from Bethesda - a word of caution - even though its a reverse commute 66 almost always come to a complete standstill from the toll-road to ballston. You may want to try getting on 50 east - which has quite a few stoplights, but at least you feel like your moving.

If you want to be there at 6.30, you'll have to leave (I kid you not) at 5-ish. Tonight with the fog & all, I left my office in Bethesda at 5:10 and got home to Ballston at 6:30 and I took the Parkway - had I taken 66, it would have been much, much worse!