PHX is one of the more layover-friendly airports for nearby neighborhoods, especially when the weather cooperates. The desert is the variable: a short walk in July is not the same as a short walk in February.
What to do with bags
If your bag is not checked through, ask the airline about early bag check. Otherwise pick a rideshare-and-restaurant plan that works with a carry-on.
Leaving the airport
Tempe, Roosevelt Row, downtown Phoenix, and close hotel restaurants are reasonable targets. Use shade, water, and short walks during hot months.
Getting back through security
The PHX Sky Train and terminal movement are manageable, but add time for heat, traffic, and checkpoint lines before boarding.