It was hit-and-miss with a lot of stores, and the butcher shops never seem to have any other cuts except for bondiola or carre. I found Jumbo always seems to have a good selection and I get pork tenderloin - solomillo / lomo de cerdo (Magret is a good brand with very very little trimming to be done - very lean). Also found some good pork-ribs from the same Magret or Campo Austral.
I do general shopping in other places, chicken and beef from the carniceria, but I always make a stop to stock up on pork at Jumbo.
Note: I've noticed that Jumbo has some days when the above mentioned items will be plentiful in the coolers and the next day they pull them out, the day after plentiful again... weekends seem to be a bad time to look, during the weekdays seems to be better. Probably more expensive but they appear to be fairly consistent with a good product.