I lived in DC for 2 yrs...working on K st ...living in adams morgan.
Just remember you will probably be taking a cab home most evenings. It's just the morning commute that you need to plan for. Buses are fine. I took circulator or 42/43. No one I know who lives&works in DC takes the metro to work. The bus is cheaper and better. The metro isn't faster since you have to walk to the stop, (at some stops..i.e. red line) go down escalators for 3 minutes to just get to the tracks, and then, go up some escalators again and then walk the distance to your office. This is all assuming you are not switching lines. The metro is designed for long-haul commutes from Virginia and Maryland. If you are living and working in/near to downtown DC (i.e. living in dupont, adams morgan, georgetown, chinatown, logan circle, u street), the places you are going to want to go will be in a very small geographic area. Even if the metro would take you somewhere closeby (i.e. going from metro center to dupont circle), you will need to wait and its expensive. I actually don't really care about the cost, I would have taken the metro if it was more convenient. I just threw it in there cause its true and others may be doing some sort of financial cost/benefit analysis or something.
And if you're thinking about non-work transportation... well, do not plan on taking the metro when you are going out on weekends. It runs very infrequently and you will have to be careful about making sure not to miss the last train. It's really easy to get cabs in DC. Also... same point as before, you will probably need to walk before and after the metro. And for general weekend stuff, half the time there is some protest or charity walk or something going on and you can barely get into the station its so crowded.
If I was moving back to DC I would probably move to the logan circle area. And I would have a car, but you would not really need one there. I would just want one cause I am from the general area and would drive to see my family. It's a great location because it is close Dupont and U street, and also close to the downtown area where most offices are. Can walk to work if its nice out, if its not nice out, you can easily take the circulator which is $1 each way. It's been a cool area for awhile but is getting cooler in my opinion. New, interesting, bars/restaurants,etc. yuppie vibe as opposed to just-graduated-from-college.
You will see a lot of listings for nice new apartments in Columbia Heights. Wouldn't recommend that area. I looked there, I had friends who lived there, let's just say I am glad I did not live there too. Way too much traffic (foot and vehicle) from the Target/Best Buy and metro, and people loitering around. Not too many restaurant/bar choices. Also the green/yellow line doesn't go anywhere that good, and like I said before, switching lines sucks.
Oh and be careful about Georgetown. It gets realllly touristy on weekends, parking is the worst, prices are very expensive, and unless you are working in foggy bottom its kind of farther away from everything else. But again like I said you will be taking a lot of cabs so not a real big deal.
The Virginia thing is a personal decision. I think DC has a lot more interesting people/places/things. You'd want a car in Virginia. I don't know a lot about living in Maryland but if you do it I would suggest downtown Bethesda. Anything else has a suburban slant. Do not be fooled by downtown Silver Spring. It might sound cool but it actually has some crime and the vibe there is more people-from-suburbs-come-for-dinner than young-people-live-here thing. I know someone who made that mistake and he moved to DC once his lease was up.
good luck! I miss DC , its the best