HappyColor - I've written this now three times. Perhaps the third time is a charm and I can actually post it.
Here is the link for the Island Explorer buses http://www.exploreacadia.com/routefinder.htm
. You should be able to get on and off at Cadillac Mountain. The loop road is best. Plan on stopping at Sand Beach, Cadillac Mountain and Thunder Hole. Some folks also like Jordan Pond where there is a nice restaurant with tea and popovers and lunch.
At the town square where you pick up the buses you will find attendants to help and advise you. Also an information center which I believe is run by the National Park Service. Do note the dates when the bus service closes down for winter. Hope you enjoy your time there.