The problem with the tourist RRs is that for the most part, nothing runs except on weekends.
Plenty of mainline modern trains to watch, though. Stampede Pass doesn't see much traffic, but Stevens pass sure does.
FYI, most of the WP&Y locos left over from WW2 were scrapped at the Auburn yard (no way you can make out where those 3-foot tracks were in the 40s now, though), and some rebuilt at the NP's South Tacoma shops, though that was torn down years ago.
You could take the Amtrak Cascades to Portland, then the light rail out to see SP 4449 downtown, along with SP&S 700 which is going through it's 15-yr rebuild right now.
-Lee
Flickr photo set of my On30 layout