If you're looking for a short ATV trail that is not too difficult to ride, check out Fremont's Camp ATV Trail. This ATV trail is just a little and for 3 miles long and even though it's not rated very difficult for navigation it only gets very light use because of the frequent snow storms in this area.
Fremont's trail is part of the Rio Grande national Forest and they do require that you have a permit displayed on your ATV at all times when riding this trail. Also, your ATV will be inspected prior to riding this ATV trail to ensure that you have a spark arrestor and a noise muffler installed on your ATV.
This ATV trail has a rough and rugged history. In the mid 1800s, General John C. Fremont took a party of 37 men and 120 mules and made a disastrous attempt to cross the San Juan Mountains in the middle of the winter while he was attempting to find in new route for the incoming railroad. They got stranded as a normal winter leaves the route almost completely impassable and they lost 11 of the men and all of the mules.
This trail is closed when snowy conditions make this area too dangerous to venture out in on foot much less an ATV, call the Rio Grand National Forest Rangers Station before you haul your ATV out to Fremont's to make sure the trail is open.