Toronto and Cancun are on the same time. Toronto uses Eastern Time (EST/EDT, UTC-5/-4) and Cancun uses Eastern Standard Time (EST, UTC-5). When it's 12:00 PM in Toronto, it's also 12:00 PM in Cancun.
Toronto observes daylight saving time while Cancun does not. During Canadian daylight saving time (March to November), Toronto is 1 hour ahead of Cancun.
Any time works! With no time difference (or at most 1 hour during summer), you can easily coordinate calls during normal hours.
Cancun is one of the most popular vacation destinations for Canadians escaping winter. Toronto Pearson Airport offers numerous direct flights to Cancun, taking about 4.5 hours.