One wishes, dear. Scuttlebutt has it that in Kaohsiung there are a couple of Paraguayan places, and there is a Paraguayan bar in Tainan, and that is as far as it goes. As you have seen, even Mexican food is rare. Yes, great business opportunity and all that jazz. I'll put up a stall selling pupusas in Shilin as soon as they fire me.
The rest of your requests, you can find in my kitchen/friend's kitchen on holidays and special occasions. No ripe plantains, though, we have to make do with bananas.
Oh, and yuicca is smuggled from Hualian when the local aboriginal tribes sell a few -even though yucca flour is easy to find here. Arepa flour? Only what we bring ourselves.
Now, can I put up a few nasty pictures to share what we are talking about?
platano is not allowed for cultivation in Taiwan due to certain fungus, so, runor has it sometimes it is sold in Vietnamese/South East Asian markets, but I've never seen them in Filipino stores. Filipino stores do carry plantain chips.
ceviche should be a no-brainer, but in my humble experience, we do not get good quality cod here, we end up with shark which turns into chewing gum when added to ceviche ingredients.