While it might seem like really obvious advice to register for the conference it's surprising that people often seem to think they have already done that, and don't realize until after the Early Bird prices have gone. It brings more money into the conference, but we are thinking of your pockets here, not ours. What next?
If you sign up for the whole deal (tutorials, conference, sprints) you will need somewhere to stay for around a week. Fortunately this year's hotel has provided us with an amazingly low price for the conference period, and if you really need to reduce costs you should consider room-sharing, a fairly frequent practice among the DjangoCon crowd. You can book your accommodation from the link in your registration confirmation email. If you don't have it then follow this link to register at the conference hotel.
You also need travel, unless you are local to the DC area (in which case you didn't need the hotel either, did you—though in fact it can be fun to stay in a hotel in your home town). DC is well-served by airports, roads and trains, so there are plenty of choices depending how far away you are coming from. If you possibly can, try to fly into Reagan National airport (DCA, just around the corner from the conference) rather than Dulles (IAD, about 30-45 minutes away) or Baltimore-Washington (BWI, over an hour away).
Then you just have to start deciding which of the many local attractions you can experience while you are in DC. Ticket, accommodation, travel and away you go!