You can change USD to any currency in Central Asia. The Dollar is still truly king here and surprisingly, Euros have not quite caught on yet. You cannot change Chinese RMB (or any currency other than USD, Yen, Euros and in some places Korean coin) in Uzbekistan and there are only Visa ATMs, which are often empty and will not work after 4:00pm. In Uzbekistan, there are two exchange rates: the official rate (which, at the time of writing was 1422 CYM to the dollar) and the unofficial rate (around 1800 CYM to the USD). You can get the unofficial rate by asking anyone in Tashkent to change money for you or by using USD when you buy things. We would recommend changing your USD and then use CYM at the official rate of 1400 or 1500.
Here is how we arrived at the aforementioned information. We carried a small amount of Chinese RMB into Kazakhstan, where we had no problem changing the currency at the Almaty-2 train station upon arrival. Kazaks took the RMB like it was the Dollar. We spent all of our Kazakh Tenge in Kazakhstan but had a bit more Chinese RMB in pocket, which we decided to convert in Uzbekistan before drawing USD from an ATM. Previous to departure, I checked that my Chinese Union Pay card would work throughout Central Asia, and it was accepted. However, not surprisingly, by the time we reached Central Asia a month later, we found that Union Pay is only accepted in Kazakhstan and then next place we will be able to use it is Turkey. Therefore, we highly recommend traveling with cash or a Visa card.
We arrived in Tashkent, Uzbekistan at 5:30am on the train and discovered no money changing office at the station. This meant we had no local money for a cab or a bus, so we set off with our 80lb packs to the hotel on foot. All along the way we spotted exchange offices that would convert the currencies mentioned in the above paragraph, but not RMB. I walked 10km in search of an ATM to use my Chinese card to no avail. I even went to the Chinese embassy in Tashkent and asked someone how they got their money out. Like typical Chinese government officials, he was not helpful and simply walked away saying, “I don’t know.”
We met a friendly local who offered to help us change the now useless RMB for CYM, but this proved futile after several days of waiting around, phone calls and promises to meet his Chinese friend. Eventually, we gave our RMB to a friend who was heading East in hopes that he could change it in Kyrgyzstan and wire us the USD. USDs are awesome here, but I can’t reiterate enough, as much as they say China is involved in the New Great Game in Central Asia, they have literally no economic presence. Don’t leave Kazakhstan with RMB. This was one of those situations that you never think would become a problem, but it was numero uno for about 5 days until we figured out a solution. Luckily, we had some great friends to stay with and found some friendly locals to help us out.