Can I charge my iPhone in Mexico without an adapter?

According to this site you should be able to use the same plugs in Mexico that you use in the USA. Keep in mind that electric supply is not always as reliable as you’re used to, so it may still be a good idea to have a surge suppressor between the plug and your phone.

You can, no adapter is needed. Although, old outlets in MX can not accomodate the newer plugs that have one prong slightly bigger, but Cancún, especially the newest hotels, should have the newer outlets like America.

You will probably be fine, depending on your hotel. However, it mught be a good idea to grab a solar charger just in case you have issues. I’ve heard good things about the Solio Bolt. It will charge your iPhone about as fast as an outlet.