San Luis, AZ has a population of 31,118 and is the 1,366th largest city in the United States. The population density is 912 per sq mi which is 1486% higher than the Arizona average and 907% higher than the national average. The median age in San Luis is 28 which is approximately 25% lower than the Arizona average of 37. In San Luis, 55% of the population over 15 years of age are married, 8% speak English and 92% speak Spanish. 35% of San Luis residents were born in Arizona, 15% were born out of state, 1% were born outside of the United States and 49% were foreign born.