Looking at biking Hawaii mid-April to mid-May on the Big Island, Maui and Kauai. I plan to start at Kona Airport and spend almost two weeks going around the Big Island, then fly to Maui for a week, then finish in Kauai for a little over a week. Disassembling and reassembling the bike to fly between the islands will be a bit of a pain but hey I'm spending time in Hawaii. Some of the roads I've heard can be a bit sketchy with blind corners, little room, and aggressive drivers. Additionally Hawaii can have a good amount of climbing being that the islands are pretty much mountains sticking out of the ocean. My plan is to start the ride on April 19th and finish on May 16th, this time of year being less busy and less expensive, also hopefully less rainy.
I have a Crazyguy journal here that goes into detail on the trip plans. There will be almost as much hiking as cycling for this tour. Camping most of the time, a few times free/stealth camping. Hawaii no doubt isn't the cheapest place to tour but I'm hoping to keep costs reasonable. I've figured costs for inter-island flights, accommodations and hiking fees to be around $700 total(about $120 of this is for campsites that can accommodate more than 1 person at no extra cost). Cost may be lower if able to get a WShower or CSurf host a few different spots. The other main costs would be fly to and from Hawaii (unless you are lucky enough to be there already) and of course food.