If you are on the Big Island, you can fish lots of places. Near the marina north of Kona are some large rocks you can go out on. Right in Kona there are some rocks in Kailua Park (west of where they have the sight seeing boats and canoes) or near the Kailua Pier. Walk past the public beach and thru the trees out onto the point. Some guys fish right off the breakwater on Alii Drive, but you have to be there on the right tide to do any good.
On the south end of the island you can go down to near Punaluu and Pahala. There are a couple of resorts with golf courses and you can go out on the rocks near the beach. Gets kind of windy, but you can do ok fishing.
Check with one of the guys at Wal-Mart in Kona and they can get you going in the right direction. They were nice to me last time I was there.
I didn't fish Hilo side. It was always raining from the Volcano and north.
Steve