I'll defer to you and Jess on the trail selection since I've never been there. I also don't know about mileage since we usually track our mtn bike rides by time. I think that I'd be hard pressed to spend more than 3 hours in the saddle depending on the climbs, sand and heat. Three hours in the saddle would equate to a longer outing depending on our stops. I'd be good with a shorter ride, too, particularly if it's blazing hot.