You should try to take a short journey on a bus at least once while you are on the island. It is very cheap but far not so comfortable like in European countries. The second popular mode of transport is a taxi. It will take more money, but a taxi driver can take you on a real excursion and tell you some lot of interesting facts about the island. The third option is to rent a car, but remember that Mauritius is a left hand side driving country.