Here's a link to the restaurant list at DCA, identifying those dining spots outside security:

http://metwashairports.com/_/File/_/shopnational.pdf

I agree with dchristiva and rzsionak that with 2 hours, you'd probably have time to cab it to Crystal City (the Crytal City Metro stop is some distance from the restaurants along Crystal Drive between 20th and 23rd Streets where most of the restaurants are located, so cabbing it would be my recommendation).

Here's a link to a list of Crystal City restaurants:

http://crystalcity.com/Dine_Shop_Sta...staurant_Guide