There's a bike trail from Pearl Harbor all the way out to Waipahu that's perpetually a candidate for expansion to Kapolei. (Kapolei can be reached now by surface streets.) You can also get downtown from the Pearl Harbor end by a mix of surface streets, bike lanes, and parks. Almost every major/secondary road on the island has a bike lane or at least a wide shoulder. The most dangerous stretch of biking is off my back lanai (Roosevelt Bridge, a 1933 two-lane bridge with very narrow shoulders) and there's a plan to build a bike trail through the gulch to bypass that bridge.
When you can't stay off the streets, most drivers are pretty considerate to cyclists although some are careless. I don't believe that drivers are a problem-- I think it's the few bad-apple cyclists who jeopardize the reputation of everone else on wheels. Pedestrians also periodically attempt to take over the bike trails but they learn pretty quickly to stay to the side and pay attention.
On weekends I also see a lot of club rides on the North Shore. The Honolulu Bicycle League is active with "Bike Ed" in the schools and with lobbying the legislature for bike-trail improvements on all road projects. IMO it's right up there with San Diego. No legislator wants to run afoul of the Sierra Club or the HBL's "aloha" campaigns so they're pretty well received.
Thanks. Sounds great.
I had no idea San Diego was also bicycle friendly. I was there several times, but was not paying attention. Anyone here from SD? Please share your observation.