If you haven't already, I would highly recommend contacting your representatives in the Oregon state senate. They are potentially looking at shutting down the Cascades south of Portland in July
Most spots are quiet zones, but there are still many good places (although pretty limited in portland) like horn alley, or by union station. To get a really busy place to watch trains, you should go to the Vancouver, WA train station which is always busy and a great place to watch trains, as it is right next to a big yard.
