Here are several maps that may help you in your journey into Mexico.
Mexico Map: This map provides a picture of the whole trip from the US border to Guasave. The Petits live in Los Glorias which is indicated as a small star at the bottom of the map.
Diagram of Buildings: Fifteen miles south of the border, a little outside of Nogales, you will stop for visas and vehicle permits. This map diagrams that area. (Note that South is up and North is down in this map).
Local Map: After you reach Guasave this map will help you get from there to the Petis in Los Glorias. (Note that North is right and South is left in this map).
Mi Casa Es Su Casa: The Petit's house in Los Glorias.