Public transportation in Lisbon is extensive and affordable. The metro is the easiest way to get around the city, with single tickets costing just €1.50. Taxis are also readily available, but can be more expensive. For day trips, consider renting a car or taking a guided tour for convenience.
If you have more time, consider spending a day in the historic city of Coimbra, or exploring the vibrant city of Barcelona which is just a quick flight away. If you have less time, consider skipping the Algarve region and spending more time in Lisbon to truly experience the city's charm.