Taking a trip out west at the end of the month and I wouldn't mind stopping by the Brooklyn Roundhouse. It's been about 18 years since I was last in Portland, is it still easily accesible? Also, are there any other spots worth seeing in Portland and Seattle?
Brooklyn Roundhouse: It's semi-easy, just keep your eyes out for trucks as the area surrounding the yard is now an intermodal terminal/transload facility. Also watch out for RR police as they have been arresting trespassers in the area.
My favorite train watching place in Portland is the pedestrian overpass right next to the Steel Bridge...You get UP coming out of Albina yard splitting east/south, as well as UP/BNSF/Amtrak heading across the bridge. The top deck of the Steel Bridge hosts the city's Light Rail "MAX" trains. Tons of action, bring a camera and a folding chair and enjoy. Be careful of bicyclists and the occasional homeless person.
Also check out Union Station, as well as the crossing at North Portland Junction, where Seattle bound trains come out of the tunnel and cross over the East-West Kenton Line.
Not sure about Seattle as I only see it when I'm working (I'm a conductor on UP), you could try out a place called "Military Road" that is opposite the Boeing field at Sea-Tac, lots of good UP/BNSF/Amtrak/Sounder action. You might plan a side trip to Tacoma, plenty of stuff going on there as well.