In Tibet, only US dollars can be accepted besides Chinese Yuan. Also shops that accept American currency are very limited and you might not be able to get a good deal for an exchange rate. Credit cards can only be used at some hotels. The Bank of China also accepts credit cards. ATM is not widely available. Exchanging your money to Chinese currency will be the best option for you, which can be done at the Bank of China.
As in the rest of China, Renminbi (RMB) is the legal currency in Tibet. Only the Bank of China offers foreign exchange services and facilities in Tibet and certain up market hotels (Lhasa Hotel, the former Holiday Inn, and Tibet Hotel). The Bank of China has a main office (0891-6835078) and several sub-branches in Lhasa, which all cash travelers' checks while only the main office offers cash advances on major credit cards (MasterCard, Visa, Diners Club and Amex). Its main office is located on Lingkhor Bei Lu 28, north of the Yak Statue and its hours of operation are 9:30 am -1pm and 3:30 - 6:00pm, Monday to Friday. Another convenient sub-branch lies on Beijing Dong Lu, between the Kirey Hotel and the Banak Shol Hotel. Its hours of operation are 9:30am-6:00pm, Monday to Friday, and 11am-3pm, Saturday and Sunday. The Bank of China Shigatse office, near the Shigatse Hotel, can provide travelers' checks exchange services also. Cash advances on credit cards are not available here. Zhangmu has two sub-branches also. Due to a lack of conversion outlets, visitors may have to change their extra RMB on the black market before their exit.