Sorry louis, but in winter you have more onshore winds than offshore.
I hvae been there in January and had onshore winds in Sotavento which was great since it is fun riding in the lagoon.
if there are trade winds, you have side off in the south, but they start normally in spring to autumn.

To get the best infos about winds have a look at
http://www.rene-egli.com that is the station right at Sotavento.

Good luck
Toby