Another thing you'll want to do is watch www.orcanetwork.org's recent sitings page just prior to heading out to see where the orcas were/are. Your chances are good since it's a humpy year and August also sounds good as the orcas will be following the humpy's...
Might that boat possibly already have some gear? If it get's rented, I'd be surprised if it doesn't already have at least a crab ring/old rod with a Penn reel....You might call the place you are renting from, and ask/see if he could scrounge up a functional old salmon rod. You could also hit up any pawnshop in Ballard/Second Wave and get a nice used rod cheap. I"m surprised nobody mentioned a diver(Deep Six)....Cheap way to get your gear down, I caught all my salmon as a kid on a Deep Six/Herring. It's also the method I've seen employed by the Coast Guard off the big boat...Ha.
Good luck....You do also have to realize that there's lots of people on San Juan that "just came out for a week 20 yrs ago".....You're gonna love it....Tom