From Lisbon take the A2 motorway south, cross the Ponte 25 de Abril, and continue past Grândola. Leave the A2 for the A26/IP8 towards Sines, then follow the N120 and local road into Porto Covo. It is a straightforward, well-signed 1h 45 drive.
From Faro and the Algarve, head west on the A22, then north on the N120 through Odemira and Cercal do Alentejo, about 1h 30. This route doubles as a scenic drive up the Vicentine coast.
Driving is by far the easiest way to reach Porto Covo and to explore the beaches and day trips once you are here. If you are flying in, hiring a car at Lisbon or Faro airport is the practical choice.