Orthopedic surgeon Mike Berkeley, white-haired and thin as the air here at seven thousand feet in Mexico’s Sierra Madre, waves to the guard from the Sinaloa cartel as we turn off the narrow highway and head down into the canyon, a four-hour drive from Chihuahua City. The young man, positioned in a dilapidated building high above the road, raises his AK-47 in recognition.Sunset is approaching on a spectacular fall evening. Rolling hills surround us, carpeted with fragrant pines, and the sky is more deeply blue than I’ve ever seen it. Mike says the small creek on our left holds big German brown trout. With a silent laugh, I wish I’d brought my fly rod. It’s not for nothing that a quarter century ago, this area…