You can drive or ride the 4 to 5 miles to the Holy Jim Fire Station. I've been a regular hiker on the HJ trail, but never ridden it. With the exception of the occasional big rock in the middle of the trail, it was in good condition atw to the falls. We made it about halfway up to Santiago Peak before turning around and at some points the trail gets kind of narrow and you've gotta watch out so you don't fall over the side, but otherwise a fun ride, specially going downhill. Trail in very good to excellent condition.
Some loose sections are somewhat exposed, so be careful.
Once you are out of the canyon bottom of Holy Jim Trail and start climbing proper, the trail is in the best condition I have ever seen. It's dated 1992. I suspect he could have continued riding, personally I was tired. Now that's gotta be some arduous climbing. They said the snow was 12-18 inches deep at the top.