banks and money?

Just like at home when you use the ATM machine--except the currency that comes out is pesos.. The exact amount will depend on the current exchange rate.

best exchange rate is at the airport.

some banks allow you to take out pesos or USD.

allways pay with pesos ,if you pay with $$$$ you will get a shit exchange rate 1 $ =10 pesos .you lose around 10 % if you pay with US $$$

Personally, I believe it is better to pay with pesos. I do, though, always bring about $20 in singles to use as tips for the first few days. You may not get any small-denomination bills when you do your first exchange, so having a wad of singles will get you \"over the hump\" with bellboys, etc. for the first day or so until you accumulate 5p and 10p coins. You can always exchange the singles or use them for tipping once you get back over the border.