Please be aware there is only one ATM in Isabela and there is no guaranty it will work during your stay.
In most places you can pay with cards. In some places there are high fees for transactions.
Upon the arrival to Galapagos you will have to pass the immigration control and pay galapagos entrance fee 100 USD per person.
ONLY CASH, there is no ATM at the arrival.
10 USD per person upon the arrival. ONLY CASH