I don't believe so since Guam is a US Territory.
However, you should probably have one to be on the safe side. If your flight gets diverted by chance, you won't be able to leave the airport to go to a hotel.
Yes, babies need a passport to travel to Mexico.
Yes, children need a passport to travel to Mexico.
Yes, infants need a passport to travel to Mexico.
Yes, minors need a passport to travel to Mexico.
Yes, you need a Mexican passport to travel to Mexico.
Yes, you need a valid passport to travel to Mazatlan, Mexico.
Yes, your child will need a passport to travel to Mexico by air.
Yes, you need a Mexican passport to travel to Mexico if you are not a Mexican citizen.
Yes, a baby needs a passport to travel to Mexico.
Yes, a child needs a passport to travel to Mexico.
Yes, children need a passport to travel to Mexico.
If you live in Mexico then no.