Hermosa Beach, CA. Online Offers. Hermosa Beach is a beachfornt city in Los Angeles County, California, United States. Its population was 19,506 at the 2010 census, up from 18,566 at the 2000 census. The city is located in the South Bay region of the greater Los Angeles area and is one of the three Beach Cities. Hermosa Beach is bordered by the other two, Manhattan Beach to the north and Redondo Beach to the south and east.