For all that DC likes to drink, people are generally cool if you decline. A couple of friends don’t drink for religious reasons and they’ll sometimes order mocktails or sodas when we’re out but we’ve never had a waiter or bartender say something and I’ve never seen anyone pressure anyone to get one. In my experience it’s not a place where everyone drinks each round of drinks at the same pace, and no one cares if you don’t want to drink.