Electricity in Mexico is 127 volts, 60 cycles delivered by a two flat prong plug or two flat plus a ground. Electricity in USA and Canada is 120 volts 60 cycles which is close enough that items that work in Mexico will work in USA/Canada and USA/Canada items will work in Mexico. However, three prong plugs are uncommon in some older installations in Mexico so items using three prong plugs might require an adaptor. Newer hotels will have 3 prong plugs. There are often voltage fluctuations in Mexico so a surge protected adaptor is a good idea. Most other countries use 220-240 volt 50 cycle electricity meaning both a plug adaptor and a transformer are required to use some items from outside North America in Mexico. Note: that cell phones, tablets, laptops and items like dual voltage shavers and hairdryers require only the plug adapter as voltage is converted internally.