We also rented cars at every port on our March cruise to Hawaii. Great idea. Of course you run the risk of being delayed getting back to your ship because of a traffic jam, accident, etc. Maui was especially crowded on their two lane roads. One word of caution when renting in Kona. The airport is quite a distance from the port and not all the companies provide a shuttle, so you need to take a $20 cab ride to the airport. I'm sorry, I forgot which do and which do not provide shuttles, but a quick call should clear that up.