I was planning on fishing the OP on April 3-4 until I heard about this fish-in. Sparkey, is this still happening? And how many people do you expect if so?

Just a word of caution - In my 8 years of fishing over there, I've learned that the locals really don't care for the "rest" of us fishing over there with our own boats etc. If you're going to do this, lay low about it. Maybe the hotel owners and restaraunt owners will like the crowd, but I'd lock everything up and keep a scout around your trucks if you're going to deluge the rivers with Seattlites. Just remember, you are a guest there. Treat your hosts that way, or they'll treat you to some bad experiences.