In Feb 2002, we stayed at Rancho Cerro Gordo, the climber resort of Kurt Smith and Mel Gutierrez (unfortunately, 1 week after we left, this partnership broke up and got very ugly, with Mel kicking Kurt out). It was a wonderful place with wonderful people. Everyone went to bed pretty early every night (usually by 10pm). Every night we could hear coyotes yipping in chorus, and every morning was a slew of cock-a-doodle-doos coming from every direction.
Note that the local places near Potrero Chico get their water from a clean spring in the mountains. You can see the adqueduct along the base of the Jungle Wall, and numerous rubber pipes bringing the water to each resident. We had no problems at all drinking water straight from the tap, or eating anything at Checo's restaurant.
The campground to the cliffs is about a 20 minute walk. In between them are other campgrounds and casitas to stay at, a deposito which is perfectly located for a cold beer (cerveza frio) on the way back, and Checo's restaurant - good cheap food, indoor/outdoor seating, and slow but friendly service and a real bathroom. Checo's also has casitas to rent. You can climb all day, grab a beer at the deposito, eat dinner at Checo's, then head back to camp. Very convenient.
Note that Tuesdays are market day in Hidalgo. You can buy everything from fresh fruit, candy and juice to used clothing and cheap tools and cosmetics are ridiculously cheap prices. Checo's is sometimes closed and the nearest place to eat is in Hidalgo - quite a long walk (at least 2 miles) on dusty roads with large cement factory trucks rushing by. Good idea to plan to cook at the campground or take your chance on local food if you can get a ride into town. The locals and any visiting climbers were very friendly and it was quite easy to hitch a ride to and from town (every time we hitched, the first car that came by picked us up).
The airport at Monterrey is a small but modern terminal. They have taxi stands with reps practically yelling and begging you to use their taxi services, a bank to exchange money, an ATM that spits out pesos with your American ATM card, restaurants, souvenir shops (magazines, dried beef, liquor, Mexican handicrafts, t-shirts, sweets, etc..). The prices are much more expensive than you'll see at the Hildalgo market. If you want to call home, you can make a collect call from numerous pay phones - just say "habla engles?" to the operator and they will switch to English. Just remember the water in the airport is not the same as the spring water near Potrero Chico. Watch out for Montezuma's revenge!
During the return, at the airport in Monterrey, they hand inspect your luggage before they check it. Polite people wearing rubber gloves go through your luggage, sometimes opening bottles, smelling lotions, asking questions. Then when boarding the plane, they randomly hand inspect people's carry-on luggage (even though you've gone through the scanning machines already). Leave plenty of time for all this inspecting.
If you leave Mexico and return to the United States, you will have to travel through immigration and customs. Immigration is very fast with your American passport, but customs may decide to further inspect your baggage. I flew from Monterrey to Houston, TX first, then connected to another flight home. I had to pick up my bags before my connection, go through immigration and customs (where they may pass you through, put your bags through X-rays again, or hand-inspect them), then check my bags back in again (that was fast, the baggage handlers see that you have tickets and the right baggage tag and throw them on a conveyor belt). Then I had to run to the next terminal to catch my connection. From then on, I am flying domestic. Make sure you plan your itinerary to leave time for all this between connections. I know of people who missed their connection home because they had long lines at immigration and customs to go through.