Story, video and photos by Cassie Hepler With newfound horseback riding skills giving me courage from sister ranch White Stallion, I ventured all the way down by the Mexican border to Rancho de la Osa in Sasabe, Arizona, about an hour and a half southwest of Tucson. And when I say by the Mexican border, I mean almost on it. You can see the wall from the ranch through the high desert grassland. Surrounded by about 120,000 acres of the Buenos Aires Wildlife Refuge, Rancho de la Osa is the most historic ranch in Arizona. You can ride the same trails as U.S. presidents and famous figures like Pancho Villa…