There are not a lot of restaurants and bars in the near vicinity of the the Capitol, especially at night, although El Mariachi has a couple of outposts for Mexican. For winter lunches, people plod with resignation to the Sodexo (formerly Sodexho!) facilities in the Concourse.
But in the good old summertime, the park on the west side, between the Capitol and the Al Smith Building, provides the best eating from street vendors. I got the jerk chicken plate today from my longtime favorite, Roy's Caribbean-American, which has a cart on the southeast side of the park (and a home base on Henry Johnson Boulevard). The dish (with rice, beans, yellow cabbage and other vegetables) was hotter than ever, but fortunately I could get an Italian ice from a nearby vendor. On the park's north side is The Big Fat Greek Truck, which I think won a Metroland poll (get the spinach pie); and, for a hamburger or other traditional fare, there's Michele's Charcoal Pit, which has excellent fries (regular and sweet potato) with some of the skin left on.