From the MK to the CR will be about 8 mins. But, you have to walk to the monorail platform, wait for the monorail to come, board, and then leave. That could be about 15+ mins.
You can walk it in 8 mins. Now.....if you really want to ride the monorail, I would recommend walking to the CR and then riding the monorail back to the MK! That will be about 20 or so mins on the actual monorail. A much nicer ride than from the MK to the CR. The CR is the stop right after the MK..not much time on it at all.