I'm in Honolulu right now. Do you care to share any tips?
Yikes. I lived on Oahu for a while. Spent a little time houseless there too on North Shore and Honolulu. There really isn't anywhere "safe" in Honolulu (Waikiki area) I can think of to camp. Lots of tweakers around. I would sleep out on the beach out towards Diamond Head a lot, but again there's lot's of tweakers so never leave your stuff unattended. Diamond Head beach is a big gay cruising beach too, so there's lots of pervs to deal with out that way. But the further mauka you head from the beach, the less of that you'll find.
You might try just mauka of Honolulu in one of the greenbelt areas like around Manoa.
I lived by Wahiawa for a while, and there were lots of homeless camped out in the woods around town there, but again.....meth.
Whatever you do, just don't try and squat or camp on the westside. The mokes don't take too kindly to haoles on that side.