My maternal grandmother was the post master in Chapman Ranch Texas when I was growing up and in addition to running a bodega that gave credit to itinerate Mexican field workers she had a giant warehouse antique shop full of stuff she would buy in shows all over south Texas or things she had on consignment from an even bigger warehouse on the King Ranch.  I later saw a pair of chairs from my grandmothers shop on the Rue des St. Peres and the shopkeeper was astounded by my knowledge of the provenance.  All that to say I inherited my love of antiques from my mother´s mother.  From my father´s mother I inherited my love of junk and bargains.

It´s unlikely you´ll wander past this outdoor space but if you are looking for old doors and or beams this is the place to start
Filagree rosaries from Dr. Guzman´s Baazar  in the Garcia Gineres neighborhood
You´ll find a couple of shops easily when you walk north of Santa Lucia Park where the xoloitcuitl Frida guards the doors
Ford searching for stuff at Julios.  It´s the best all round spot for uncovering treasure.
the other shop on calle 60 that is not often open but has a few nice things and where I found a beautiful silver necklace from Taxco circa 1940 for a song… and a dance.