Hi all,
I'm planning to spend about 4 days in Washington DC next May or June. We wish to do all the usual tourist stuff- however hotels in DC itself seem very expensive.
How realistic is it to stay in the outer suburbs and use the metro? Ideally we are looking for hotels below 150$ a night, same side as Dulles and in a nice area

It depends on how far out you want to stay. The futher away from DC you stay--even with the Metro--the more inconvenient it is going to be. It also means you will spend a larger percentage of your time commuting and less time actually being a tourist.

There are hotels along the Metro at stops like Rosslyn, Courthouse, and Ballston that would be fine. That seems to meet your criteria.

I wouldn't stay anywhere that would require I take hotel shuttle, have to walk more than 10 minutes to the Metro, or you have to drive and park.

I agree with Mike T that you should be able to find some accomodations within your price range in the places he listed. (For example, I saw that rooms in mid-June at the Key Bridge Marriott in Rosslyn are available for $139.00 per night.) You might also check out Crystal City.
BTW, if you are not familiar with the Washington D.C. area, Rosslyn, Courthouse, Ballston and Crystal City are all sections of Arlington, Virginia. They are all nice areas very near the Metro with lots of hotels, shopping, dining and, of course, office buildings.
The commute by Metro should be easy and fast. For example, from the Ballston Metro (the furtherest of those listed from Washington, D.C.) to the Smithsonian Station takes just over 15 minutes.

Thanks for that info. What time does the metro stop at?

Thanks

Metro runs til midnight Sun-Thurs, later on Fri-Sat.

All you need to know about Metro:
http://www.wmata.com/

The nicest thing about the Key Bridge Marriott is that you can walk right over the bridge into Georgetown.