I just got back from Maui. The best of all the Hawaiin islands, IMHO. And incredibly bike friendly. I could not believe how wide the biking lanes are there.

Ah yes, and Haleakala. A group www.gocyclingmau.com climbs this mountain road, also dubbed as the longest paved climb on the planet. Thirty six miles, and 10,023 in elevation (the famous Mont Ventoux on the Tour de France is a mere 13.6 miles and a 5,336 in elevation).

High season is December to March due to all the Whales that breed during this time and that can be seen. September is a great time, the traffic was not bad and the weather was amazing. The wind does get crazy in the afternoon.