Disney's Magical Express?

I know that people take Disney's magical express to their hotel. However, would you be allowed to take it to another hotel? As I mentioned in another question, my sister is getting to Disney the day before, and having dinner at the Polynesian at 5 (my flight arrives at 3:15). I need to meet up with her before I can check in to my hotel. Would it be possible to take the bus to the Polynesian instead of to my hotel or is that strictly not allowed?