In any coastal region where you find limes, you'll find ceviche, going by one name or another. In Mexico, it's frequently made with a combination of scallops, shrimp, conch, and octopus (the last two usually precooked to the point of tenderness), and those are all good fish for the mix. If you can find spanking-fresh fillets of your local white fish, you can use that here too, although scallops alone are easy and fabulous. If you happen to have a couple of different colors of bell peppers, mix them; it'll make the dish really sparkle.