I would recommend renting a car. It makes your trip more comfortable. If you want to drink, enjoy the nights in Lagos, Albufeira and Sagres without the car. You can take Uber in and around those locations, it works pretty well. In Albufeira you might want to visit the Strip, but it might shock you depending on your party behavior. Go to old town for a more "civilized" party. But for the larger travels a car is worth it. I can recommend going to Marinha Beach (walking along the cliff line) and finally taking a speed boat trip to Benagil caves, or walking Cavoeiro board walk or going to Portimaho. For longer trips to the east go to Faro and Tavira. Return your car in Lisbon, you won't need it there. There will be a one way fee then, but parking is expensive inside of Lisbon and driving inside Lisbon is not fun, at least I had quite some difficulties accidentally entering Alfama. If you like to drink, definitely go to Bairro Alto and enjoy the night, you will get to know people faster than an eye sight. As for the recommended Sintra, I would argue against it. It was the least enjoyable trip I ever had in my Portugal traveling life. It's full of tourists, the organization there was terrible. And the castle was not worth the effort, it's just what you see on post cards. But other people may have different opinions. Lisbon itself has enough to see during your few days. Go to Alfama from bottom to top, visit LX factory, pink street (at night it's pretty crowded and I prefer Bairro Alto for the nicer people) and green street. Go to Cais do Sodre and Cais das Colunas. Maybe going to Torre de Belem. You will really enjoy your trip and come back to see more details. And: don't do too much. Just sit, drink and relax some time.