I agree, never rent the scooters! You can bring it back without and trouble and the people you rented if from and say there is something wrong, then they charge you a LOT of money, either that or you go to jail. Not to mention traffic is horrible in cancun, you could end up in a serious accident! Just ride the buses, those are enough fun as it is, hahaha
Done the Jungle Tour in 2005. Cost about $30 through our hotel rep. Driving 2 man speedboats at 60mph is awesome. Through the jungle and out into the middle of the lagoon for some snorkelling at the reef. Lasts 2-3 hours. Well recommended! I'm gonna do it again in a few weeks.