Alejandra Cavazos has a soft spot for strays. Growing up in McAllen’s Mexican sister city, Reynosa, she took in feral cats and loose dogs, a practice she stopped during her time at university in Monterrey. Cavazos received a PhD in international affairs there before moving to McAllen with her husband, Rafael Ramirez. Ramirez and his family own the Rio Grande Valley chain Tortillas Aries. At the shop’s McAllen location at the corner of Pecan and Ware, Cavazos; her business partner, Antonio Monzon; and Ramirez have set up La Prieta Mamona, a taco trailer named in honor of one of Cavazos’s pets, La Prieta, a black Lab–pit mix. “It’s dreadful, because supposedly rescue dogs are so grateful,” she says. “Well, [La Prieta] is not. She has the…