The different campuses thing is interesting...You're only there for the first year, then for the second year, the entire class is in Seattle. After that, you do "regional" rotations, so the WAMI peeps go back to their home state, and OOS and WA residents go around WA. So, really, its only the one year that you'd potentially be in Pullman or Spokane (and apparently there's talk of having another site in Yakima soon) for the first year. Just think of it as one more hurdle. And if you really want them to love you, rank Spokane first. Something like 80% of incoming MS1s rank Seattle first, so obviously not everyone gets their first choice. The next most popular is Pullman (god knows why since its in the middle of nowhere), and then Spokane. All three are on major university campuses (UW-Seattle, UW-Spokane, and WSU-Pullman) although Spokane is somewhat smaller than the other two. So, given all of that, if you ranked Spokane first, they'd probably love you, and it is only for the first year.
I asked about this topic ad nauseum when I interviewed last year, so if you have any other questions I can try to answer them.
Good Luck!