Michele,
I lived in New Jersey for a number of years and had access to the Met. Now I live in Virginia and visit the National Gallery. There is no comparison, ... but then is any place like the Met?
However, eventhough it doesn't begin to compare with the Met I still think it is worth a visit. When I go to the conferences (or other cities for different reasons) I try to always stay and visit whatever museum is in that city, there always is some original piece that is worth seeing in person, and I figure it may be my only opportunity.
Regarding the National Gallery. It is in two sections, the East Building and the West Building and they are connected by an underground Concourse. The East Building tends to have more modern art. With the exception of Special Exhibits (often held in the east building) I generally don't care for the East Building. I prefer visiting the West Building. Although the collections are not as extensive as the Met, there are still some excellent works worth seeing. In particular, if you go there be sure to check out the "Shaw Memorial". There is an excellent relief sculpture of the first African-American infantry to fight for the north in the civil war. The piece is beautifully done. It is on the main floor of the west building.
The West Building also contains DaVinci's "Ginevra de' Benci" as well as some excellent Frans Hals, Rembrandt's and other dutch and flemish painters. There are also some wonderful pieces by the impressionists.
Someplace else to consider in DC and within walking distance (if you don't mind walking) of the National Gallery is the Freer Gallery of Art. They have the world's largest collection of work by Whistler. However, they can only display portions of the collection at a time because of space limitations.
Plus there are some excellent non-art museums to visit in DC.
Hope this helps, and I look forward to meeting you and others at the conference!
Mary