Unless you're planning at staying at your hotel for the duration of your stay, you'll definitely want to rent a car. If you like the feel of the sun on your head, and don't mind the occasional rainstorm, get yourself a convertible. Unlike Oahu, there really isn’t any public transportation to speak of here. It will probably rain at least once while you are here, but it is usually a quick, warm shower. In can also pour. Traffic can get very bad at times also. Patience is the key. Don’t leave any valuables in your car. Just leave the car unlocked. That way, anyone who wants something will poke around, find nothing, and move on. Often, if the car is locked, they will break the window on the theory that you have something valuable in there or else you wouldn’t have locked the car! Then you have to pay for fixing the window! Because cars belonging to tourists may be targeted by thieves, you may want to consider "localizing" your rental car. Hang a kukui nut lei from the rearview mirror, and keep any travel information in the trunk.
If you’re considering making the famous drive to Hana, keep in mind that it takes a LONG (6-8 hours, including stops to drink in the waterfalls) time to get to Hana and an equally long time to get back, or to drive all the way around Haleakala! If you get carsick, you may want to consider skipping this, although the drive is beautiful and lush.
The above photo is of Wailua Falls, one of many lovely waterfalls on the road to Hana. Another option is just going half way down the road to Hana - you won’t see the pools, but you will see many lovely waterfalls and have time to do a bit of hiking. By the time you get all the way to Hana - you realize that you have two options - driving all the way back, or driving all the way around Haleakala. Both options are long drives. Leave EARLY in the morning (aim to leave Kahului by 8 am) and realize that you will most likely be following a long line of cars - all going slow and looking at the beauty of Hawaii also - so if you can’t stand driving slowly on curving roads - just skip this. But the whole idea of Hawaii is to slow down the pace - so relax and enjoy it. While seeing Hana's lush sights from a convertible is breathtaking, be aware that the Maui sun is more intense than what you're used to on the mainland. Maui is closer to the equator, and your regular sunblock regime won't cut it. A bad sunburn can ruin your vacation, even in a place as perfect as Maui. So don't feel bad if you get "stuck" with a regular car. You'll be less likely to burn, and that air conditioning feels mighty good after a long, sweaty hike.
Some of the roads are unpaved and pretty rocky and narrow, so take it easy and consider renting a four wheel drive if you can. Yes, a sedan can make it but it can suffer a lot of wear and tear and the rental car agencies really don't like you doing that!
