It is easy to exchange the currency in the city. Almost in every street there is an exchange office.
Please, note that worn out, washed out, torn, cut, and old banknotes are not accepted.
Exchange offices won't accpet them as they won't be able to sell such bad banknotes to others.
Also they don't like to take too small notes, like 1, 5 dollars and coins are NOT taken even by banks.
Make sure your bills are not too old.
From foreign currency only USD and EURO are accepted, the other currency are difficult to be exchanged.
You can buy souvenirs, pay to driver etc in USD or Euro in cash.
Of course, the best is to have local currency, as in restaurants and supermarkets they don't accept in foreign currency.
Credit cards are welcomed and accepted in many places. Payment for the tours are ONLY by cash.