Yes, there is Dahain Party in DC:

Here it's:

America-Nepal Society
invites all the community members and friends of Nepal
to join
Dashain - Tihar Mela 2008

On
Saturday, October 18, 2008
Time: 12:30 noon to 7:00 p.m.

Venue:
Knights of Columbus
5115 Little Falls Road
Arlington, VA 22207-1899

Entrance fee: $5:00 per person
(kids under 10 are free)

Special attractions:
ANS Election Committee Announcement
Exhibits & merchandise for sale
Nepali food
(details will be posted soon)
Cultural program

Beverage Cash Bar
available by Knights of Columbus