To get around Phoenix, you will need a car. Only the major downtown areas (Phoenix, Scottsdale, and Tempe) are pedestrian-friendly. Don't expect to nab a rental car without a reservation, especially from January to April.
Roads in Phoenix and its suburbs are laid out on an 800-square-mile grid. Grand Avenue, running 20 miles from Downtown to Sun City, is the only diagonal. Central Avenue is the main north–south axis: all roads parallel to and west of Central are numbered avenues; all roads parallel to and east of Central are numbered streets. The numbering begins at Central and increases in each direction.