Well ill say good luck since chinook wont take a fly, if i understand correctly, since their only goal up river is to spawn so they dont eat natural food sources while spawning. That why bobber and eggs are so commonly used in the area. I know that Cabella's has egg patterns to purchase for use on fly rods, and boy wouldn't it be fun to hook up with a 15+ pound chinook on a fly rod?
Coho might go for flies i'm sure, but you cannot legally angle for these fish right now anyways as retention is closed for them in the siuslaw.
What you would probably catch a lot of are sea-run cutthroat trout, which there is a healthy population in the river right now.
If you looking to have a good shot at catching and retaining a salmon you may want to ditch the fly rod and bring a rod to rig up for bobber and egg. Although i'd be curious how cabella's egg pattern "flies" would work when spotting and targeting an active spawning ground.
I'll be hitting the siuslaw friday , though it may be too high still. Lake creek which feeds into the siuslaw is also a good alternative if its flowing too strong. On the same highway up from swisshome.