The greatest danger to travellers here is not altitude sickness...it is walking in the open market downtown. The open-air stalls here are mainly run by very, very aggressive Tibetan women who get nasty if you do not buy something. One even spit at us when we did not buy their product!! Instead, I recommend the stores behind these stalls. Most of these are run by chinese who will give you a much better deal and also be much more polite. Otherwise, have fun and enjoy the temples.