I use Travelers Checks
My ATM charges 3% for an exchange when abroad; there is also any ATM fee, mine I think is a dollar, any fees on the ATM's end - if any, and the exchange has not been as favorable as Travelers checks.
Also, what do you do if it swallows your card? Someone suggested bringing two. The maximum withdrawl is sometimes too low for my needs.
However, most places I try. either won't accept my Travelers Checks or you do wait in line or the clerk takes forever to check if your Checks are any good.
Luckily I have used Marco's Cambio in Santiago for years, get a good rate and because they know me it goes smoothly.
Cash is best. I bring half my money in cash, but since I have known people to have beien robbed every once in a while, I don't risk everything with cash.
Best wishes for your travels!