Weslaco, TX has a population of 39,021 and is the 1,064th largest city in the United States. The population density is 2,060 per sq mi which is 2025% higher than the Texas average and 2174% higher than the national average. The median age in Weslaco is 33 which is approximately 3% lower than the Texas average of 34. In Weslaco, 57% of the population over 15 years of age are married, 26% speak English and 73% speak Spanish. 67% of Weslaco residents were born in Texas, 12% were born out of state, 1% were born outside of the United States and 20% were foreign born.