Casa de Oro-Mount Helix is a census-designated place in San Diego County, California, USA. The CDP encompasses several neighborhoods in unincorporated parts of the cities of El Cajon and La Mesa as well as part of the unincorporated community of Spring Valley. The CDP gets its name from the neighborhood of Casa de Oro, which straddles the line between Spring Valley and unincorporated El Cajon, and Mount Helix, a prominent hill in unincorporated La Mesa. The population was 18,874 at the 2000 census. Casa de Oro-Mount Helix apartments for rent comparison page shows most up to date rent information on Casa de Oro-Mount Helix apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.