You can choose to do the Safari (where you travel around the WWAMI region) or you can choose to do a state track (doing all your rotations in a particular state). You'll have priority for your respective state (for example, an Idaho WWAMI student would have priority for the Idaho track), but if you have connections/strong ties to other states, that can put you higher on the priority list for rotations outside your state. Unless you have something tying you down somewhere (kids, sick family, etc), you'll likely travel every 6-8 weeks. (Lurking MS2s/MS3s/MS4s can correct me if I'm wrong)
You can set up a "home base"-a place where you will cover your own housing/transportation. Barring Seattle + your home base, UW will cover housing/transportation.
Length of rotations vary by what you're doing. They're usually between 6-8 weeks. The elective rotations are shorter, somewhere around 2-4 weeks.