This is a wiki crowdsourced by the Monzo Community to help you travel with Monzo.
Just like Wikipedia, anyone can edit it to help out others. If you have any tips or feedback for visiting Mexico with Monzo, please feel free to edit this guide. You can also add a comment or question below — someone will then incorporate your comment into the main text below and then delete your comment. To create your own “Monzo in …” guide if one doesn’t already exist, just copy this template into a new post and write away!
Safe travels! 
Currency
Mexican Peso (MP)
Monzo users pay the Mastercard exchange rate with no added fees. Always remember to pay in the local currency to get the best rate!
Card Usage
Monzo cards will work at most payment terminals (shops, restaurants etc.) and ATMs that clearly display the MasterCard logo. It’s always handy to use the MasterCard ATM finder if you need to withdraw some cash, which can be found here.
Other Monzo users have mentioned that it is sometimes tricky to find a MasterCard ATM, but most shops and restaurants accept MasterCard payments. (This is also the way to get the best exchange rate).
It is also possible that some ATMs will operate with Magnetic Stripe technology. You can allow magstripe ATMs on your account for 24 hours in the app. This means your card will work at mag stripe ATMs as well as chip ATMs for the next 24 hours. After this, it will default back to declining 
You can turn on magnetic stripe support for ATMs and terminals in the app’s Settings! If you need the magstripe turned on for more than 24 hours, let Monzo know!
Payment and withdrawal limits
Monzo passes the Mastercard rate directly on to you (we don’t make any money from doing this!), and you can find details of the current rates here (select 0.00% as the “Bank Fee” to get the correct rate).
As for ATM withdrawals abroad, you have a £200 free allowance per 30 day rolling period and there will be a 3% charge for international ATM withdrawals thereafter (which I’m sure most people are aware of).
Crowdsourced Merchant Data
The Monzo merchant data is sometimes incorrect e.g. map shows the wrong location or the name of the place is incorrect. Please submit improvements through the Monzo app so it can get better for future visitors.
Miscellaneous
In general people seem to have edged more towards card payments rather than ATM withdrawals while using their cards in Mexico.
Also worth noting that there maybe difficulty withdrawing cash in the Morelia, Michoacán area.