Winds along the coast most often come from North. In the Willamette Valley where Amtrak runs, it is more variable.
It is an agricultural area. There are some interesting sights along the way such as an airplane museum with the Spruce Goose. It isn't stunning awesome scenic like the coast further west, but I found it pleasant riding and did a number of "day ride down...train back" type rides when I lived in Portland. I also essentially rode Vancouver to Eugene each year but broken into different weekends - so definitely enjoyed the riding.
Portland is a larger and busier city. Portland has its own bike culture and events, e.g. Sunday parkway closures, a Bridge Ride, a Naked Ride, etc so depending on interests and timing would be a different type of stop. However, also a
lot busier.
Thanks! I was actually thinking instead of getting off the train at Portland instead: The train arrives around 4pm, and the Empire Builder doesn't depart until around 4-ish the next day, so I can ride around the city and the River Gorge a bit.