90 will run just fine. Not fresh, but probably not broken rings either.
I am sure you've probably already read about the trick of putting a teaspoon of oil into each cylinder to see if the number come up or stay the same; if they come up it's rings, if there's no difference it's valves.
A couple tricks an engine builder taught me about taking compression readings:
(1) Take all the plugs out.
(2) When cranking the engine, open the throttle so the cylinders get full air.
(3) Try the reading 2 or more times to make sure (this is actually basic metrology).
(4) At higher altitudes, you can never get sea level numbers (this is basic physics).
The absolute pressure in Denver is about 12 PSI, versus 14.7 at sea level. Expect compressions numbers to drop by that ratio (12/14.7=0.8) or to convert Denver readings to sea level divide by that number (90/0.8=113). A nominal 150 PSI engine should read about 120 in Denver.