Recently got on the air using the 2 m repeater at Mt Ord. I haven't found many other popular repeaters yet and wondered what others in the Phoenix area are using.
I can't speak to repeaters in your particular area, but repeaters in general tend to be busy at different times of the day.
Around here, we have one repeater that is busy for the morning commute but quiet the rest of the day. This same repeater tends to be a popular weekend spot too. There is another repeater that has a lunchtime net every day at noon. It is very lively and gets a surprising amount of check ins for being in the middle of the day. The reason why is because most of the regulars are old retired guys.
There is a repeater just a mile or two from my house that hardly anyone uses and I can easily hit with a handheld. Seriously...sometimes I scan it all day and hear only an ID. Myself and a few friends have informally made it our own private repeater! It can go for days and have no traffic other than us.
As you get more into ham radio, you will find out that repeaters are like bars. Each one has its own personality and vibe, with a core set of "regulars" who come by often. My advice is to not necessarily default to the nearest or most popular machine. Shop around, spend a few weeks getting a feel for the kind of crowd that gathers at each one and the times when traffic is heaviest.
Over time you will get something positive in all of them but find yourself gravitating towards one.