My 2 cents worth.
We use only debit cards from US credit unions.
We only get money from cajero automaticos at bank location whenever possible - we go out of our way - no stand alone kiosks - true in US as well as Mexico.
We almost never pay fees even if the machine says we will be paying a fee - whatever system we are in has arrangements of some kind I do not understand.
We almost never use credit cards unless absolutely necessary - true in US also.
We never get large amounts of cash - true in US also. The most we get is $5,000mx at a time - in the US maybe $300US. We are allowed $500 US but could raise it if we want. We don't need much cash in Mexico. Our biggest expenditures are usually fueling our Bus which would be in the $2,000mx to $3,000mx range.
Of all the bank machines we have found we think CI banks have the lowest rates - while Bancomer or Santander down the street are charging as much as $80mx the CI bank is charging $15mx. Here are lists of some CI Bank locations for those interested.
http://www.cibanco.com/storage/Sucursales_CIBanco.pdf
http://www.cibanco.com/storage/suctddjul20101.pdf