Yes you can, and they will take the Mickey Dollars.
In 2001, my family and I stayed from Dec. 24 through Jan 2 and we had booked the room in Feb. of 2001, and each month we saved and turned the cash for Disney Dollars so that we would have enough for the room to be paid off, I will say it was alot of Disney 10s and 5s as they dont go above 10s, but My brother and I arrived at the WL at 9:30 am on Dec, and we paid off the entire room in Mickey Money. I say go for it, if want.
Larry