The perk is good for texts sent while in Canada to any international number.

You will get charged roaming fees if you try to use your phone while in Mexico.

As for the perk, if you just switched to one of the pick your perk plans then you’d get it right away. If you were already on one of the pick your perk plans but had a different perk then it would kick in starting at the beginning if your next billing cycle.

I added this free perk and was charged on easy roam despite the wording being 

“International SMS: Send and receive unlimited international SMS and MMS to and from Canada free of charge”

I assumed to and from Canada would have meant that I could send text messages to Canada from the US.

So far I have been unable to contact Koodo.