South from Co Springs Rt 25, exit Walsenburg, go west on 160 then north on 150. It's much prettier to go over thru Salida and down 17 to Alamosa, but much more time consuming.
Weather can really catch you off guard. Be prepared for rain and lightning and also really hot conditions in the summer.
Tallest dunes in USA reside on 84,670 acres in the Sangre de Cristo Range in south central Colorado. They rise 750 feet from the valley floor.