Seems like some of us aren't from Hawaii, so a few words of advice from my last visit, to any fledgeling slack key players making the trip:
1. Take a lesson or two! I schedule some time with Ozzie Kotani, and spent a great couple of hours learning and chatting. He also sent me some tabs as well. What a great guy, and man, you should hear him play! Post to the alt.music.hawaiian newsgroup (if you're not familiar with newsgroups you can access them through groups.google.com), and someone should be able to get you in contact with a musician. I've head Ray Kane, Led Kaapana and others will give lessons.
2. Alt.music.hawaiian is also a good place to find out who'll be playing. The week I was there I got to hear Led Kaapana & Hui Ohana. Got a few CDs autographed, and talked story with Dennis Kamakahi a bit. It was a great week!