Rent your own wheels, Hilo
We always book a car online before we leave home. We check all the rental companies and go with the best offer. It is important to rent ahead of your arrival especially during the holidays, there are not enough vehicles to meet the demand
We leased a car and had to take a jeep instead. They called it an upgrade but at the price of gas on the islands, we didn't really think it was an improvement.
All rental offices are located outside the terminal.
Traveling to Hawaii isn't hard at all but you will need cash to get here. I've met people who saved up for a very long time (years) just to come here for a few days. Paradise is quite expensive I'm affraid but if you budget right, you can swing some deals to get here. My suggestion is (especially if you're from Las Vegas) to check with local travel agencies on the West Coast or in Japan (if you're from there). You may very well find that travel here is much easier money wise than if you were to book it on your own. Many agencies offer package deals including car and hotel at affordable prices.
A word to the wise however, as with many car rental agencies, there are clauses in the contract. Please take the rental insurance as many specialty vehicles (Convertables, SUVs, Off Roaders) are not covered by your own in the event you crash.
For the US mainland travelers... Hawaii is not a foreign country (yeah I know, people come here thinking that!!). You will need your drivers liscense or else you're stuck walking around in town. In Hilo, everything you need for shopping, food, leisure, is located a few miles south of the airport.
You can fly into Hilo, if you are coming from another Island. Or fly into Kona, then hire a vehicle. ------- Two Airlines to choose from... 'Aloha Airlines' and 'Hawaiian Airlines'.
A car or motorbike would be best, as in all the Hawaiian Islands. I was with a Tour Bus, and it was great, but I didn't get to see all that I would have liked to see. I really did enjoy this tour, it was very informative, and our driver, Alan, was a lot fun ;-)
He even stopped for a second or two, if I wanted to get a picture of something ;-)