These are the common choices that locals choose for Breakfast inside the Cancun Hotel Zone:

-VIPS (behind the Convention Center, across from the Bull Dog night club)

-Sanborns (in the Flamingo shoping mall)

-Obviously you can have breakfast in your hotel

In downtown Cancun locals have infinite choices for breakfast:

VIPS, Sanborns, Toks, Calfornia Cafe, El Porton, Bisques de Obregon, Cafe Andrade, El Cafe de la Nader, etc.