When asking to ride up in the front (which, by the way is limited to 4 people), if they tell you it's full, ask to wait for the next train. It's only a 5 minute wait, and well worth it.
When I was a monorail pilot, tons of people would ask to ride up front, but when it was already taken, very few were willing to wait the 5 minutes for the next train. Then they'd complain that they'd been there 5 days, and never were able to get up front. It's probably the shortest line at Disney, and very well worth it.