The only long line at the DMV we don't mind is the one outside El Trucko. That's the name regulars have given the white truck parked weekdays on Metropolitan Grove Road alongside the Montgomery County Motor Vehicle Administration in Gaithersburg.
The truck's owner, Gregorio Garcia, has been serving up satisfying roadside tacos for ten years, after arriving in this country from Nayarit, a province in northwest Mexico. He and sister-in-law Nayarit Garcia make all the fixings--meats, beans, and salsas--at home and assemble the tacos to order at a counter on the side of the truck.
Best bets are the marinated pork, carne asada (grilled flank steak seasoned with cumin, vinegar, and salt), and barbacoa, fatty beef that's been steamed in plastic bags wrapped with foil, making it juicier and more flavorful. You won't see avocado or sour cream--these are authentic Mexican tacos--but Garcia keeps some behind the counter for customers who insist. Wash them down with a Sidral Mundet, the Mexican drink that tastes like fizzy apple cider.
Open Monday through Friday.