Interlaken, CA has a population of 6,738 and is the 5,314th largest city in the United States. The population density is 687 per sq mi which is 168% higher than the California average and 658% higher than the national average. The median age in Interlaken is 34 which is approximately 5% lower than the California average of 36. In Interlaken, 58% of the population over 15 years of age are married, 31% speak English and 63% speak Spanish. 56% of Interlaken residents were born in California, 7% were born out of state, 2% were born outside of the United States and 35% were foreign born.