Bring hard U.S. currency with you, as the country's few ATMs do not work with bank cards outside of Bhutan or India, and credit cards are only accepted in a few tourist shops. (Where your guide will steer you, since they get a commission.) Given the nature of pre-paid all-inclusive trips, you won't need to carry much more cash than for tips, souvenirs, or alcohol in your money belt. A hundred dollar bill will get you a higher exchange rate than a smaller bill or traveler's check. The Bhutanese currency, ngultrum, is pegged to the Indian rupee; those are accepted in some places.