Well the reason is...
the reason you don't use ATM is because you are then at the mercy of the banks to give you a fair exchange rate. Usually they are close and it is not a big deal...but I have had experiences where the rate given to me was 3 pesos per dollar different and then you pay an ATM fee of...in my case...3.75 usd per ATM withdraw. I was paying the bank 70 dollars a month in ATM fees and figured out that I was paying 200 dollars more than I needed per month. Also, if the machine takes your card you cannot get it back. You have to go to your bank in the USA.
I have tried to cash checks at an exchange house and I have been denied. So please tell me what the trick is?