The lowest cost (aka most bang for your buck) for currency conversion tends to be at the currency exchange stores at the airports. Banks usually add in the "fee" to the exchange rate and it varies by bank, but tends to be between 3-4%. If you don't use all of your Pesos, save them for the next trip instead of selling them back or you'll be losing 6-8% on the total conversion when all is said and done. That same fee is built into ATM charges on top of any ATM usage fees.
We always tip everyone with a $2 bill, I've been told repeatedly that they pool the tips anyway and they remember the $2 bills, even when we have't been there for a year or so. I was also told that they think the $2 bills are good luck. Once we took a bunch of the Susan B Anthony $1 coins (long story) and some people thought they were fake, plus being heavy, so we didn't do that again.
I downloaded the app - I am an IPhone guy and there is an IOS version as well. Sure looks amazingly easy to use. I never thought about an app to convert. I always got out my calculator and did the math myself. Thanks @Donna & Tim for the recommendation.
