Hi Sasha!
Yes, in Portugal as a whole and in Porto and Lisbon (the 2 biggest cities) you won't have many issues speaking English. Most young people speak English and you'll find that portuguese have a knack for understanding everything - in the worst case scenario (you don't speak any ENglish, they don't speak any English) I'm sure you'll be able to come across to others.
That being said, try to understand a couple of words and sentences beforehand, so everything will be as smooth as possible.
Hope you enjoy your staying