The current class is all Denver based. Of course these things are cyclical, but right now it appears that Denver staffing is on the decline (just as we finally made it to a 4 and 3 schedule for January). I expect things will stabilize again, though.
Changing bases is not as simple as saying "I want to change base." You do get to list a base of preference, and that gets you ahead of new hires. But there is no guarantee as to how quickly the change will occur.
If you are considering Boutique, I'd recommend being willing to start at a base other than your first choice if at all possible. Be careful, though. MSP and PDX seem to have commutable schedules, other bases not so much. I guess it depends on how much you want the job.