If you haven't seen the Goat Canyon Trestle, it's a very worthy destination. I think this description takes you over the top after climbing out of Mortero Palms (also a neat area) but I got turned around when I tried that and did a different route to the railroad (check my triplogs and gps routes in the area) Cool history.
[ Mortero Palms to Goat Canyon Trestle ]
[ photoset ]
And if you've never stopped to see the hot springs at the desert view tower right on I-8, it's, well, something.