I was waiting for my turn to pay for my favorite nopal and chile tostadas with flax seeds at the tianguis on Friday when I noticed another woman buying a new-to-me cheese. She told the stand owner to give me a taste, and then I bought some myself. I also made him repeat the name about 5 times so I could look it up when I got home.
The cheese is queso morral. It had a spongy look and texture, but it's really good melted in a quesadilla (especially a real quesadilla that's fried with fresh masa). He had plain cheese and one with a bit of spice. I got some more today.
Morral means bag or backpack in Spanish.