After extensive googling, there weren't a ton of trail descriptions in english for La Huasteca (which makes sense) so we pretty much showed up and winged it based on what we could figure out from the guard at the park gate, via our pal Bill's rough translation skills. Mostly, "Don't climb to the big cave, you need ropes, super dangerous, don't do it, something about a road second to the left."
After walking along the park road for a bit and taking in the beautiful vistas from the bottom of the valley, we started up the trail at the "second to the left" place. Turns out there's a parking lot with a big "segundo" sign, so that was easy enough to figure out. The trail went directly up a hillside marked by spray painted arrows (no switchbacks or fancy trail construction here) and had some awesome views from the city at the top. I'd estimate it was about 600ft of gain over half a mile or so, but pretty steep with lots of slippery rocks.
When we got down, the guys hadn't had their fill of hiking yet, and still really wanted to try to find the crazy cave we had seen on Mountain Project, so we headed up a different trail a bit further down the canyon. Lots of gully scrambling followed by a small amount of cactus bushwhacking got us to the base of 2 little caves. I opted not to go up into the caves, and got to watch a family of falcons hunting from the cliffs while the guys checked out the interiors. Due to the super slippery, breakable limestone I wouldn't opt to climb here, but definitely a cool spot for a view.