Welcome to Portugal, hope you enjoy it.
When you come to Porto, make sure to eat a francesinha. Try bufet fase. If you want to eat some of the best hotdogs anywhere in the world, go to Gazela. Try to go at lunch because they tend to close early.
Also, in the downtown area, make sure to visit Livraria Lello. Its one of the most beautiful bookstores in the world. You have to pay like 3 euros to get in, but if you buy a book they will deduct the price by that amount.
Also in that area, its a really good place to drink and party at night. Lots of bars with all kinds of music available. If it doesnt rain, there should be a fuckton of people in those streets at night.
If you like art, check Serralves out.