Rancho San Diego, California landscape and open-space maintenance. Rancho San Diego is served by the Cajon Valley Union School District and the Grossmont Union High School District. Steele Canyon High School and Valhalla High School are the primary schools in this location. Rancho San Diego is also home to the Cuyamaca College Coyotes. Rancho San Diego, California Rancho San Diego is a census-designated place (CDP) in San Diego County, California. The population was 21,208 at the 2010 census, up from 20,155 at the 2000 census. The area was developed as subdivisions beginning in the 1970s. Rancho San Diego is located at (32.765985, -116.921477). According
San Diego County, California of the Treaty of Guadalupe Hidalgo in 1848, ending the Mexican–American War. This treaty designated the new border as terminating at a point on the Pacific Ocean coast which would result in the border passing one Spanish league south of the southernmost portion of San Diego Bay, thus ensuring that the United States received all of this natural harbor. San Diego County was one of the original counties of California, created at the time of California statehood in 1850. At the time of its establishment in 1850, San Diego County was relatively large, and included all of southernmost California south