I've been hiking here for many years. I am addicted to the summit trail and occasionally hike the circumference trail. It's a great workout and offers nice views of Phoenix. The summit trail can get really busy on the weekends. Fortunately, with the warmer weather just around the corner, the crowds should start to thin a bit.
When I was on my way down the hill on Monday I saw someone walking up the trail with a pit bull on a leash. I Informed them that there are no dogs allowed on the summit trail and they turned around and went back down to the parking lot.
Three things to remember: 1) stay to the right 2) the person going uphill has the right-of-way and 3) no dogs on the summit trail