score:5
A bicycle trail runs the entire length of the Algarve. (I am not affiliated with any business at that link.) Part traverses the Parque Natural da Ria Formosa, and is also a pedestrian path. It's completely flat, so if intense mountaineering is the goal, not a good recommendation. But if you are interested in either flowers or birds, it might be an informative and enjoyable outing.
The southwest tip of Europe at Sagres is also worth getting to. Same trail.
The typical tourist stuff includes enormous and inexpensive-for-Europe fish dinners.