Granite Hills is a neighborhood in east El Cajon, San Diego County, California, United States. The neighborhood comprises areas within the city limits of El Cajon as well as areas of unincorporated San Diego County. The unincorporated part of Granite Hills is included in a census-designated place by the same name. The population of the CDP, which does not include the part of Granite Hills within the city of El Cajon, was 3,246 at the 2000 census. Granite Hills apartments for rent comparison page shows most up to date rent information on Granite Hills apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.