PayPal is of the largest global payment gateway solutions. They operate in almost every country including Mexico. It is easy to use and set up. PayPal has a very powerful API which can be used to customise the payments based on the merchants requirement.
Openpay payment gateway charges the lowest transaction fee in Mexico. It has no set-up cost, integration or configuration cost. Openpay charges 2.9% $2.5 MXN on Visa and Mastercard transactions and 4.5% + $2.5 MXNPayment Gateways (Mexico)