you might want to try the sol duc up in the park. i seem to remember getting come rainbows up there when i was a kid. i would still have to say that the best bet would be the elwha though. my dad and i fished that river for about a week and got some really good fish. be careful if you throw streamers out there though, that river has some SERIOUS bull trout in the deeper holes and runs.
good luck
-Connor