I usually come here when I am trying to make my own homemade tacos. They offer different kinds of meats and meats that have already been marinated.
The butcher shop is located in the back of the grocery store and you take a number until they call you. Usually it is quick service and sometimes it's a little hard to look for something specific but they have most meats! They also sell nice flour or corn tortillas that you can use for tacos.
If you're hungry, they also have a kitchen in here. Pretty decent stuff. They have a salsa stand too. I honestly wouldn't come here for regular grocery items, like things you would find at a Smith's or Albertson's because you may get a better deal over there. However, Mariana's is great for all of your Mexican food needs!
One of my favorite things to get here is the homemade salsa and also homemade sour cream.