Definitely one of my favorite areas!
Viana de Costelo (big beach at Cabedelo, go to point B and head to beach: http://goo.gl/maps/O8wes
) has a great bay that usually offers nice waves (and can be super flat water in between the spread out waves)
Esposende (Ofir) has a really great flat water spot in the river (go to point B and walk in on the board walk to the spot on the dune on the riverside to setup/launch: http://goo.gl/maps/4OIXZ
I'm sure even right near Afife you can get good waves (pending the tide schedule) along the coast.
The big city beach (nice place) at Matosinhos (Oporto) is great with S winds and offers good waves too if you happen to be in Oporto. Local Porto kiters: http://www.facebook.com/groups/163449700353308/
I'll be there for the month of June...I'm stoked.