Short trips from El Potrero/Monterrey

I'm going to be in EPC for a while and was wondering if anyone had any suggestions for a side trip of a few days, climbing or non-climbing, within a reasonable distance from Monterrey? Anything one should really see in that part of Mexico?

I haven't been down to EPC since Christmas / New Years of 99'-00'.
I don't know if it is still there, but we drove to a very cool hot springs that is about 30 miles from Hidalgo. the road is very rough in spots and you should take a 4-wheel drive if you can. It will take you a couple of hours to get there and a couple more to get back, so although it is a short distance, it is a full day activity.

On the way, you will pass very interesting / cool old churches and old buildings. Additionally, you go through small farming ranching villages that are truly poor and seem like they are hundreds of miles from modern cities instead of 30 or 40 miles. Take extra food (canned goods, etc.) as the kids will come up to your vehicle and beg for whatever you can give them. The hot springs (like most of Mexico) was under construction when we were there, but was super cool...
If you are interested in this, I may have the hand drawn map that Kurt Smith gave me 8 years ago. PM me and I will send you a copy if I can locate it.

You can do a canyoneering trip up in the mountains near Monterrey that passes through caves. Quite a few actual caves up there, too. The area is called Potrero Redondo I recall.