I lived in PHX for a number of years, and was an avid mountain biker. One day, just a few miles from my home, I was grinding up a steep climb with my head down, focused on the trail. I glanced up, just in time to see the back half of a mountain lion, slink into the scrub brush ahead and to my left. I had no weapon, and was in a quandary. Keep going, knowing I could just crawl up this steep climb, or turn downhill, and race away and risk triggering it's "prey" response. I stood there for maybe 10 minutes trying to locate it but never did, and eventually rode to the top of the climb and down the other side. You couldn't have driven a straight pin up my backside with a sledge hammer, I was clenched so tight.
Two other incidents not involving me. A lady walked on to her patio to enjoy her coffee (again in the PHX), caught movement from the corner of her eye, and a mountain lion was drinking from her pool!
A mom was at the school bus stop, at the border of Mesa and Apache Junction (eastern suburbs of PHX), with her young child and several other kids. Glanced back over her shoulder and noticed movement in the brush. Lo and behold, a mountain lion stood observing them. They relocated the bus stop!