I believe some of the reviews I've seen for La IsleƱa are a bit unfair. I didn't find the establishment dirty at all. It is smallish, but absolutely jam-packed with all kinds of wonderful Mexican food, you just need to search a little bit to find what you need. Aisles are also pretty tight, but there's no lack of selection!
Prices are extremely reasonable; I bought 2 lbs of fresh, home made ceviche for just over $6.00. The owners are extremely nice, the meat selection is extensive and I can't wait to return for some more ceviche!