There's not a lot of details up yet at http://openeverything.wik.is/Washington%2c_D.C. but feel free to contact Steve, whose contact info is on that site. Also, if you'd like to discuss the event with the global group, feel free to join https://groups.google.com/group/open-everything-discuss.
I'm based in Madison, so I can't speak to DC plans extensively, but if you have questions about Open Everything more generally, feel free to contact me.