I don't know how long it would take from Coronado to MK. But give yourself ~30 minutes from MK to Poly via monorail. You will have to go through security, while others walk straight to enter MK, you will turn left toward the monorail entrances. Make sure to take the Resort monorail if you want to get dropped off right infront of Poly. If you accidentally get on the Express monorail, you can get off at the Transportation and walk to Poly.