Its true that ATMs are popping up in playa all over the place...every year more and more, and I use them all the time but its worth knowing that if you access a foreign account and there is a messup with the machine you will need to wait till you get back home to clear it up.
About 12 months ago I went to an ATM on 30th to withdraw 7000 pesos from my canadian account. The machine made that whirling noise that I love so much but did not open and then shut down....no problem says I, and off to another machine I went where i was greeted with Balance unavailable or words to that effect.
The bank that "sponsored" the machine was zero help, and after some online research i found that this would be true anywhere...such issues must be cleared up by your home branch.
eventually it was sorted and the money returned to my account but I am definately wary now.