Where should we stay based on…?

Hi Guys Me and my partner have just booked via easyjet a week in Lisbon at the end of July. We have never been to portugal. We are both in our late 20s but not exactly ravers but do like a bit of life. We want to see the sights of the city centre but also visit the beach a few times and have a chill. We have not booked out hotel yet and prefer to eat out so will need to stay somewhere with bars and restaurants. With all this in mind where would you advise us to stay before we book a hotel? Thanks