La Presa is a census-designated place in the East County region of San Diego County, California, United States. The population was 34,169 at the 2010 census, up from 32,721 at the 2000 census. La Presa belonged to the neighboring Spring Valley CDP from its inception in 1970 through 1990. It is still considered part of Spring Valley in informal usage and addresses in the CDP continue to use the name Spring Valley. It was named after Sweetwater Dam.