San Carlos, TX has a population of 3,112 and is the 8,620th largest city in the United States. The population density is 1,721 per sq mi which is 1675% higher than the Texas average and 1800% higher than the national average. The median age in San Carlos is 32 which is approximately 6% lower than the Texas average of 34. In San Carlos, 56% of the population over 15 years of age are married, 8% speak English and 92% speak Spanish. 64% of San Carlos residents were born in Texas, 9% were born out of state, 0% were born outside of the United States and 26% were foreign born.