IN FRONT of the Jokhang temple at the heart of the Tibetan capital, excited members of a Chinese tour group pose in their new cowboy hats and snap photos to post on their microblogs for friends back home. Not far away, others pose in Tibetan garb in front of the Potala palace, traditional residence of the Dalai Lama. Many have experienced the recent Chinese pop-culture craze for things Tibetan, such as “The Tibet Code” (an historical thriller written in the style of “The Da Vinci Code”). Now they want the thrill of adventure travel themselves, and their numbers have soared, even as the number of foreigners visiting the region has declined.