The Portuguese coast provides some very acceptable windsurfing conditions accompanied by the tendency for the winds to be reasonably constant in force. These winds mostly average between Force 3 to 5.
A particularly good windsurfing beach is the famous "Guincho" east of the city of Lisbon. The waves here can range from one to three metres but an under-current has to be constantly considered. Another popular location is "Praia Grande" on the north coast.
In the Algarve there are many windsurfing centres on the beach that will rent equipment.