San Ardo, California. San Ardo (formerly, San Bernardo) is a census-designated place (CDP) in Monterey County, California, United States. San Ardo is located 18 miles (29 km) southeast of King City, at an elevation of 449 feet (137 m). The population was 517 at the 2010 census, up from 501 at the 2000 census.