some suggestions! woogie's from dc
there is a fun beatles exhibit at the Museum of American History.
The best small museum in my opinion is national geographic, which is on 17th just beow Dupont Circle. Lots of good eats there -- Bistro du Coin, Johnny's Half Shell, Pizzeria Paradiso, Tabard Inn (for breakfast esp., or drinks at night near the fire), Al Tiramisu. Luna Grill (hearty breakfasts). Pick up a city paper when you get to town (free, published on thursdays) which has all the happenings. -- live music, open mic nights, poetry slams etc (check out washingtoncitypaper.com for some advance ideas). The Kennedy Center has (I think) free shows at 6:30 in the great hall -- lots of local acts.
on the weekend if the weather is good check out Eastern Market (7th and C SE, E. Market metro, blue or orange) On Saturdays its a farmers market, on sundays more of a flea market. oldest continuously operating farmers market on the east coast. saturday morning they make the BEST blueberry buckwheat pancakes in the entire world but get there EARLY.
for opinionated eating advice visit chowhound.com and click on midatlantic boards and post the details of your trip -- people will give great advice on hotels, activiteis and of course food, but you must be specific about your preferences.
you can also check out swing dancing at Glen Echo, an old amusement park west of town (need a car) -- I think on saturday nights they do a lesson, then you dance at 8 pm. very fun.
for night time fun check out U Street (between 16th and 13th NW); there are cool places down 14th too.
have a great time -- DC is a lovely city. and if you can't find anyplace to watch Bachelorette, get in touch!