On shorter distances they usually don't stop. If a pit stop needs to be made by someone in the leading bunch, then everyone usually joins in and backs off the pace. Those that need to stop, just need to hurry up and join the bunch again. If you get left behind, tough. During this years Tour de France, Lance had to make a pit stop at same stage and most of the bunch stopped aswell. His team mates waited up and helped him back into the bunch. I noticed that most of them didn't even get off their bikes. They just unclipped one leg and did their business! My wife found it hillarious ;D
Personally, I make sure that I make a pit stop as close to the start of the race as possible (in terms of time, not distance ;D ) I also try not to eat anything that will upset my stomach or encourage bowel movement in the two days leading up to the race. I usually eat lotsa pasta during that time (carbs).