I agree...do not rent a scooter. Roads are very narrow, hilly and winding. Traffic very heavy with lots of buses, trucks and drivers who will ride on your bumper. As mentioned, they also drive on the wrong side of the road. Even riding the bus is scary. Get a daily transportation pass that covers buses and ferries...best way to get around the island.
To give you an idea of how narrow the roads are...buses do not have mirrors on the left side. Reason why, the would be knocked off in the first five minutes of driving. They drive that close to walls, posts, signs, etc. mirrors don't stand a chance of surviving