I traveled for three weeks through southwestern China (Yunnan, Sichuan, Guizhou and Guangxi) and parts of the Tibetan plateau in Yunnan, Western Sichuan on altitudes between 2.800m-4600m (9,000-15,000 feet).
Week 1 - Yunnan: Lijiang, Baisha, Tiger Leaping Gorge, Shangri-La, Meili-Snow Mountain
Week 2 - Sichuan: Chengdu, Western Sichuan (small group tour) and Dujiangyan
Week 3 - Guizhou and Guangxi: Zhaoxing and Tang'an and Xingping near Yangshuo.
I highly recommend visiting this part of China, especially as public transport with high speed trains is inexpensive. Also traveling with local buses in the mountain regions of Yunnan has been easy. The most challenging part was finding a tour group that would accept foreign tourists in Western Sichuan (departing from Chengdu).