I agree with LucWise. I have flown through MTY many, many times over the years. The airport is very simple to get around, passport control typically goes fairly quick, and by the time you are through with Passport control, you're baggage (if you check any) is generally waiting for you.
Getting a cab is simple. As LucWise said, just through the sliding doors after baggage claim is a taxi stand with a touch screen terminal. Piece of cake!!
There are some great restaraunts in Monterrey and the city is relatively safe! Enjoy your trip!