Tight, technical, and rocky the Alta Trail is a fun but challenging downhill ride. You can ride it uphill but the seemingly infinite rocky switchbacks mean there will be a lot of hike-a-bike for all but the most fit riders. If you want to save your legs you can park at the San Juan lookout and ride the road up to where it meets Alta and enjoy the ride back down to your car. Be aware that there is a lot of cacti right along the trail so long pants or shin guards would be a good idea.