Prescott Valley is a thriving town of about 42,000 population in Yavapai County, Arizona, United States, just east of Prescott.Prescott Valley was the seventh fastest-growing place among all cities and towns in Arizona between 1990 and 2000. According to the 2010 Census, the population of the town is 38,822.rescott Valley was the seventh fastest-growing place among all cities and towns in Arizona between 1990 and 2000.