I flew into Mexico City last year in December. I had two backpacks with me. One had a 35mm film body, two lenses, 20 rolls of b&w film. Most of the film was a gift for a friend. The other bag had a digital 35mm body, two lenses, a laptop and associated cables and gadgets. At customs my bags were inspected, I was only asked if I was planing on selling the laptop in Mexico. Nothing was asked about the camera gear and the customs officer certainly did not count the rolls of film. So, no problems.
Have a fun trip.