The currency in Kyrgyzstan is the Kyrgyz som (KGS), and is usually not available in currency exchanges outside Kyrgyzstan.
ATMs are widely available in main cities and usually distribute Kyrgyz som and US dollars. You should pay with KGS but USD is a universal currency, and may be accepted in certain situations. ATMs sometimes have a maximum som withdrawal limit. This varies from bank to bank, but is often around 10,000 KGS. ATMs are also usually available in smaller towns, though it may be more difficult to withdraw dollars outside main cities. Credit and debit cards are widely used around the country; VISA is accepted in most places, but MasterCard is sometimes not accepted. Payment by QR code is also common. Travellers’ cheques are not normally accepted.
Bring cash if you plan to travel to rural areas where ATMs may not be available.
US dollars are the most easily exchanged foreign currency. Notes from before 2007 usually are not accepted or subject to additional charge if changing to Kyrgyz som.