Fishing in Hawaii can be alot of fun, and you should be able to find a spot not to far from where ever you are staying. While in Maui a couple of years ago, I had the opportunity to observe the locals fishing. The spot was not too far from where we were staying, and I walked down to chat with the locals every night. Don't be afraid to aproach local fishers, and start up a conversation. I found it MUCH easier to do than here....
Let me say that the locals are VERY friendly, and willing to share their methods, stories, and even their catch! In the area where we stayed, local fishermen could congregate each night after work to fish. They would each bring food, and have a pot luck dinner and BBQ. I was invited to join in and never experienced such hospitality from people I didn't know.
When you arrive, there is a free fishing newspaper available in the airport....pick one up, they are a great read, and give information about local hotspots, and some of the more impressive catches (giant trevally up to 300 lbs!). There are a number of fishing methods that are similar to what we do here, for smaller fish....but I found the surf fishing particularily interesting. Fishers would first "whip" the shallow water with a ultralight rod and reel to catch bait. (bring your own light spinning outfit) Bait used were these very small colored lures (see picture below), which I saw for sale in a local shop.
BAIT!
After the bait has been captured, the big surf rods come out.
A typical Rig
(I noticed that these could be rented in the local tackle shop) Using a superbraid of some type, the fisher casts out a huge weight that acts like a anchor, terminating on or near the reef...he then reels up to tighten the line. Next a "leader line connected to your live bait via a large hook is attached to your main line by a snap-on-loop...and the loop, and the bait slide down into the water.....from here on in...it's a waiting game. The prized catch is giant trevally, but many other species are also caught including some big sharks......I went back each night hoping to see a large trevally caught....only to miss the action by 5 minutes on my last night in Maui.
baby shark about to be released (sorry about the poor pic!!)
On a side note, there is this whole thing about custom reels in Hawaii....check out their reels...some of them have some very cool modifications.
As for a fly rod...well i didn't see any the entire time I was there, however, I don't see why you couldn't use one.....and all the small fish you catch would be much appreciated as bait by nearby fishers. Only problem is the wind....it's a rare day that there is no wind.