There's an intermittant bike path from Vail to Edwards. Google maps' bicycle route shows it pretty well. When the path ends, ride US 6 to Dotsero where the Glenwood Canyon bike path begins. It continues to Glenwood Springs.
Yup. Parallels I-70 the whole way.
On the other side of the Divide, you can follow I-70 most of the way to the bottom of Loveland Pass, then follow the Summit County Trails up and over to Vail. I don't know how construction on the Twin Tunnels is going to impact the bike path along Clear Creek from Hidden Valley to Idaho Springs, however.
West of Glenwood there are also sporadic trails that parallel I-70 as well as US6. Maybe not the best riding but it's direct. And I've ridden far worse.