Finally, after 2,000 road miles and 16 months, I took my Trek 3900 xc MTB off road, in a place called Rose Canyon. What a blast!!!
I only rode a bit more than seven miles, and it took an hour. I found myself WAY over my head a couple of times as the trail got VERY tricky. I fell off the bike once, and had some close calls several times. The terrain varied from hard pack dirt, to three inch deep sand, to gravel/rock. Sometimes those rocks were a couple inches in diameter, sometimes five and six inches, sometimes smooth and round, but often with sharp edges as well.
The trail was out in the open much of the time, but sometimes in a small forest area, and sometimes so narrow I was getting scratched on both sides by thorny bushes. There were some small climbs, and a couple I couldn't ride up or down because they were so steep and tricky.
I saw maybe three people out walking the trail, and two other bikers, both of whom appeared to really know what they were doing. This was my first time and my lack of skills became apparent immediately. I tried to take a few pictures (see below) but couldn't really capture much of the Oh My God twists or turns in the trails for some reason. I learned that a trail can get nasty in a heartbeat, and that shady branches (coupled with sunglasses) can hide a big problem up ahead quite easily. I also learned that some trails just come to a dead end, as the bushy picture below illustrates. That trail just stopped.
I guess I'm saying that I learned it's NOT like riding on the street! D'oh!!
But it was fun, and I got LOTS of exercise, and some sore muscles that ordinarly aren't sore, and a dusty bike to boot. I'm glad I went for this ride.