Portola Valley, CA has a population of 4,550 and is the 6,880th largest city in the United States. The population density is 500 per sq mi which is 115% higher than the California average and 452% higher than the national average. The median age in Portola Valley is 55 which is approximately 53% higher than the California average of 36. In Portola Valley, 74% of the population over 15 years of age are married, 85% speak English and 2% speak Spanish. 46% of Portola Valley residents were born in California, 38% were born out of state, 1% were born outside of the United States and 15% were foreign born.