The not to be missed between late July and Mid August is carpetfuls of wild flowers with snow capped mountains as back drops. Mt Raininer National Park is the perfect place for such views. Hurricane Ridge in Olympic National Park is another great place and be sure to hike the short pleasant ridge hike. Every time I went, I wondered if I were in the movie "Sound of Music".
Of all the national parks I have visited in US, I think Olympic National park is the most diverse, dynamic, and beautiful national park of all. Be sure not to miss the ocean beaches of Olympic National Parks.
Have seen migrating salmon on hiking trails and even neighbor's backyard streams but don't remember when. I believe it depends on the species.
People don't fuss much about salmon around here since there are too many of them.
Ballard Lock in Seattle is a good place to see migrating fish from the ocean to the lakes/rivers upstream. It's also fun to watch boats go by the locks from fresh water to salt water. You will also see big fish jumping out of water at Ballard lock. Here is a link:
http://www.destination360.com/north-america/us/washington/ballard.php
Don't know anything about cheap travel packages.