Hi, Jakke,
If you eat fish, you will have absolutely no problem getting by in Portugal. As Heidi describes, freshly grilled fish is easy to find on the menu and absolutely delicious. Unlike their neighbors to the east, Portuguese cooks do not put meat in their vegetable dishes. Instead, the fish is always served with freshly cooked, totally unadorned vegetables. Most common are carrots, broccoli, and couve (something like collard greens). And the potatoes are delivious, nothing like the industrially produced potatoes I get in the supermarket in the US. (And while I was searching for the translation for couve, I found this list of vegetable translations from Portuguese to English, which might help you.)
http://www.sk.com.br/sk-veget.html
Cod/bacalhau is never served fresh in Portugal, they only serve dishes made with dried cod. There are many, hundreds in fact, types of bacalhau dishes. Gomes de Sa (with eggs, onions and potatoes) and Natas (kind of a bacalhau cooked like macaroni and cheese, with lots of cream, a real comfort food, if a bit heavy) are the most popular. Heidi, could the dish you describe be Bacalhau Ze do Pipo?
http://portuguesediner.com/tiamaria/bacalhau-a-ze-pipo/.