Monte Rio is a census-designated place in Sonoma County, California along the Russian River near the Pacific Ocean. The town of Guerneville lies east of Monte Rio, and Jenner is slightly north-west. The population was 1,104 at the 2000 census. Monte Rio apartments for rent comparison page shows most up to date rent information on Monte Rio apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.