St. Augustine South, FL has a population of 4,930 and is the 6,545th largest city in the United States. The population density is 3,109 per sq mi which is 959% higher than the Florida average and 3331% higher than the national average. The median age in St. Augustine South is 47 which is approximately 13% higher than the Florida average of 42. In St. Augustine South, 51% of the population over 15 years of age are married, 92% speak English and 4% speak Spanish. 38% of St. Augustine South residents were born in Florida, 53% were born out of state, 3% were born outside of the United States and 6% were foreign born.