Apparently you can! This came up a few months ago here on the DIS and those in the know said it's limited to 4 people and they are still doing it!! You just have to ask the operators when you get there and be willing to wait because there may be parties in front of you wishing to do this as well. It's a great experience. Your countdown says 3 days until DL- have a blast!
We just asked the CM on the platform when we arrived, and he had us stand aside while the rest of the train loaded. DF was wearing her Birthday button, so that might have helped.
If a party is already in the front, riding in the back is pretty cool also. We just did this in January, and loved the view. Plus, they allow more than 4. It was my adult daughter and myself, and they let 3 teenagers ride with us.
DH and I have ridden in the front a couple of times. It's worth a short wait and is definitely different that riding in the rest of the train. You get a panoramic view of the parks, and the whole experience is more interesting!
We did this just a couple days ago from the Downtown Disney station.We were in line but stopped as the monorail was full. Once it departed were first in line and asked if we could ride in front. They said as long as the people in the front of the cab got out we would have first dibs. People came up behind us and asked if they could ride up front and they said "fist come, first serve". The people in the next monorail got out so we were able to get in.