Not sure what the name of the hostel was in Haleiwa with the 3 night min. but I found this one- http://www.backpackers-hawaii.com/ and it looks pretty good. I can't vouch for it personally because we're lucky enough to have 'family' on Oahu who we can mooch off Slippahs is right about the surf though, however the North Shore is a very relaxing place to get away from it all and especially quiet during the summer. Enjoy!