If you are in the city, you must find the time to visit the MARCO museum in Monterrey, N.L. Three exhibitions happening during this summer... (I really enjoyed 2 of them). Strongly recommend Cardiff & Miller and CARLOS AMORALES. It is worth the time... and not expensive at all; actually (I'm no modern art expert at all), these exhibitions could be well seen at MOMA in NYC or similar.
Consider 3+ hours to see all... I did it during a business trip in the city and was refreshing. Helped me in setting my days of work that followed the visit.
Raúl