Most places take visa or mastercard eg. gift shops, snorkeling tours, restuarants. Another widely used method is traveller's cheques. However, you need to be along the proof of purchase when cashing them at the bank yet most establishments here accpeted them as cash payments
Something to consider when using your credit card for purchases...although it is not legal and goes against their merchant agreement, many businesses will charge you an extra 5% when using your credit card to pay for things. Chan's doesn't, China Town doesn't but Friendship will. Most of the tour places will also.