Hey Apoorva, There are many ATMs in Port Blair .... so no need to worry about drawing money there ... Almost all restaurant and hotels do accept cards ... But if you are visiting islands like Neil and Havelock ... it's always better to have cash in hand ... there are ATM s in Havelock also ... but you need to stand in longer queues to draw money ... See that very few places cards are accepted in Havelock ... Happy Travelling !!!
Hey Apoorva, ATMs are available in Havelock Island but due to satellite connectivity problem they may not be available for use at some particular time. I will suggest you to carry enough cash. It is also suggested to book hotel and ferry in advance and you may not be requiring more than 5000 INR per person for two days stay.