Mexico

I am planning a 2-weeks trip to Mexico to search and document street hand-paints and storefront signs in Mexico. As these hand-paints and street signs are are a vanishing popular communication form, my goal is to build an online platform where I can document and geotagg these hand-paints and share each “personal” story hat is related to it.
In two weeks time I want to find as much as possible of this art-forms. Mexico has a tradition of hand-painted street signs which means one can find them anywhere. But are there (next to Mexico City, which I will visit) specific, places that are known for its big concentration of these works?