Even in the middle of winter, oahu nights are warm enough to sleep in with a 0 degree sleeping bag or a blanket. The island has a campground on the north east coast that sells camping permits.
[header] How to be a " homeless " backpacker in honolulu [title] Find alternative accommodations. [step] Hostels and backpacker inns are not cheap (and motels don't exist! ). You may want to consider camping to avoid blowing all of your budget on lodging.