San Luis, CO has a population of 678 and is the 17,672nd largest city in the United States. The population density is 1,212 per sq mi which is 2334% higher than the Colorado average and 1238% higher than the national average. The median age in San Luis is 47 which is approximately 30% higher than the Colorado average of 36. In San Luis, 53% of the population over 15 years of age are married, 31% speak English and 69% speak Spanish. 87% of San Luis residents were born in Colorado, 10% were born out of state, 0% were born outside of the United States and 2% were foreign born.