I've spent several seasons in Mex. in the past and always loved it. Fly to Monterrey for sure, take a cab or bus to Hidalgo, it's less then an hour away. It's a mellow walk from town to the entrance of the Potrero where the camping and rentals are, you'll probably get a ride from passing climbers anyway. Once there, no need to have a car. The weather will be fine, year to year it can be chilly or hot but always climbable. It's a great place, easy to find partners as finding partners goes. The food is great, market day in town twice a week, tons of fresh food and cheap. I always brought a water filter down with me. Most people were not filtering and thought I was crazy. I figured it was a worth while precaution. Bring a full 60m rope and a couple first fulls of draws and you're set for gear.