I agree with all the above. Monarch has plenty of passing lanes going up from Salida--for whether you are passing or being passed. Going through the canyon between Pueblo and Salida is a very curvy route and require attention but is very scenic along the Arkansas River.
Nice places to spend some time: Salida and Buena Vista, Gunnison and Crested Butte, Black Canyon of the Gunnison, Ouray, and Mesa Verde. Buena Vista, Crested Butte, and Ouray are not ON US 50 but are well worth going off route.
I hope you are not just "going through" this great part of Colorado.