I don't mind tourists as a photographer, but many parts of town become intolerably crowded whenever school is out somewhere. It gets hard to walk down the street, so you have to stick to parts of town that tourists can't find (basically anywhere but the National Mall, Georgetown, Capitol Hill, DC Waterfront, Old Town, Tidal Basin, Arlington Cemetery and its surrounds, Crystal City, Pentagon City, and Bethesda). But that is a lot to avoid.