All of our routes have mileage information and more about the route itself on our website. You can go to this link for the Utah Cliffs Loop: http://adventurecycling.org/routes/utahcliffsloop.cfm
Mid-April is most likely too early to ride that loop. Some of the roads are at high elevation and will still be closed by snow. I wouldn't recommend it before early to mid-June, depending on what kind of snow year it is.