It is true that the Rocky Mountain Division, which has the second largest membership (second to the Eastern Division), has the most full-time instructors, and (I believe) the highest percentage of Full-Certified instructors.
It's interesting, though, because in most ski schools, even in the larger Colorado Resorts, Full Certified instructors are very much a minority. One statistic I do not know is how many of Colorado's instructors are not even members of PSIA--many new instructors are not. And some smaller ski schools are not PSIA Member schools. (As noted in previous threads, PSIA membership--and even moreso, certification--is not a requirement for working at "PSIA Member" ski schools. Some ski schools put a much higher emphasis on PSIA membership than others.)
For what it's worth, you can always request a Certified, or Full-Certified, or whatever you want, instructor at the ski school desk. Some ski schools will comply. Others won't, or can't. But there's no harm in asking.
Not all certified instructors wear their pins, partly because they break or fall off and get lost easily, and they're not that inexpensive to replace. For those wearing pins, the design is the same for all three levels of certification, but Level 1 is a bronze and black pin, Level 2 is red, blue, and silver, and Level 3 (Full Certification) is red, blue, and gold. An "ISIA" pin (International Ski Instructors Association)--a white oval with the "ISIA" logo--is available to Full Certified instructors from most skiing nations, and you'll see a few of those on jackets of some of the international instructors working in the US.
It pays to be an educated consumer!