WM Camlin (Seattle, WA) is within walking distance to Amtrak's King Street Station. It isn't a particularly easy walk (hilly) ... but we've done it while dragging the luggage along.
The problem with taking Amtrak to Seattle, and this is likely true elsewhere as well, is the time the train arrives. Passenger trains are routinely bumped to the side to let cargo trains by so you can't count on the train arriving on schedule, especially on longer routes. So while the schedule says you will arrive at 8pm, it is more usual to have it arrive at midnight and that area of town is not a place you want to be walking around after dark. Definitely plan on paying for a taxi of some sort.
A friend is a big fan of trains and takes them most places. He has joined us on occasion taking the train and we have learned, from past experience, that he needs to arrive at the meeting place the day before to allow for the delays in the train schedule. He will then grab a motel for the night and meet up with us the next day. It's worked out well.
Many of the western destinations are also places you will want a car, so taking the train to a major nearby city and then renting a car opens up most places. The train that goes along the southern border through Palm Springs, Yuma and. Tucson would a good option with easy taxi options to get to the resorts or rental cars available.
The zephyr goes through the CO rockies including Winter Park and Granby where there are timeshares or rent a car to access some of the other areas along the interstate. Salt Lake City is a short drive to Park City and all those timeshares, etc.
Sue