I'm the grandchild of Clotilde Preciado Covarrubias, daughter of Martina. My mother is Teresa Sanchez, nee Nielsen Preciado. I too saw the family tree in the Museum of Anthropology, was too young to appreciate it, but remember seeing my mother as the tail-end of the line (we, her children, were all born in the US). I would dearly love to be able to have a copy of it now.
Clotilde was born in 1895 in Juchitlan, Jalisco. She had several siblings -- among them, Maria Isabela, Juan Jose, Francisco, Victor, Julian, Trinidad...I think there were more. My mother, Teresa, was born in Mexico City in 1930, but her elder sister, Marta Nelson, was born two years earlier in Port Huron, Michigan, USA. I have other odds and ends of information based on aunts, uncles, and second cousins a-plenty that were around during my childhood.
I would be fascinated to hear more and to amplify the skeleton of my ancestry. Please, do write!