Do a search on ATMs and you will find plenty of info. From my reading there are machines but it's easier to bring lotsa cash and some TCs.
Your resort should be able to arrange diving for you. I'd ask them what their procedure is - AC doesn't seem to be lacking in the dive shop arena, but I know one shop I contacted wouldn't dive w/ me b/c I was staying on the other side of the island... You'll probably dive w/ the shops that are closer to your resort.
Not sure on the playoff's question.