I live in Zihuatanejo, a town on the Guerrero Coast and the locater put the Postal Code for Xochihuehuetlán, Guerrero (a very small community in the mountains on the other side of the state almost to Puebla) about 400km away to the east. Putting the correct postal code put me further away! The "This is approximately where Google thinks 40880, mx is" when I put in the correct Postal Code didn't even get the right state - it put me in Guadalupe de Corrientes, Zacatecas some 700km to the north.
So the data bases are incomplete or just plain wrong.
At least it got the right state and right country initially!