Jason Mandel: That was my experience at the Plantation, too. I went last December--two weeks before the Mercedes--and it was cart-path-only. At times it was definitely a bit of a drag...the cart paths tend to be positioned on the high side of the fairway, and the slope will bring your ball down the side of the hill most of the time. If JAL is going in July, though, this won't be a problem for him.
Of course, the trade-off for this cart-path-only inconvenience is that they weren't sending anyone out after about 12:30 PM or so. The Plantation was in absolutely AMAZING shape. Perfect conditions for golf.
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As for the Hana Road, self-drive vs. tour bus, my wife and I had a blast doing it ourselves. If you plan on driving it yourself, make ABSOLUTELY CERTAIN to rent a convertible at Kahului Airport. We saw all kinds of amazing stuff (birds, flowers, etc) in the canopy right above our heads that I would imagine people in the tour buses miss. And we alternated driving so that we could each take in the scenery.