18F is at GSA headquarters (1800 F St NW); USDS is across the street from the White House, next to the White House Conference Center on Lafayette Square. GSA has a very reasonable informal dress code. Khakis and button down shirt would not at all be out of place; shorts would stand out.
A big part of this job is interfacing with other government agencies, which means you're going to visit their offices.
A big part of this job is interfacing with other government agencies, which means you're going to visit their offices.