You'll need some cash in local currency but you can also use your credit card.

你将需要一些当地的货币现金，但也可使用信用卡。

Many countries charge departure tax in U.S. dollars rather than local currency.

许多国家在征收离境税时收取美元而不是本国货币。

They also have a need for local currency.

他们也有获得当地货币的需要。

This would increase the value of the local currency.

这会引发当地货币增值。

Hence they sell the dollars and buy back their local currency.

因此他们卖出美元并买回他们的本国货币。