If you have your own boat or windsurfing gear, sheltered Playa Panteón [1] would be a good place to put it into the water, although the neighboring headland may decrease the available wind. Calm mornings at Playas Zipolite [2], San Agustinillo [3], or Mazunte [3], or afternoons, with more wind but rougher waves, might also be fruitful.
Links:
[1] http://www.moon.com/destinations/oaxaca/pacific-resorts/puerto-angel/sights-and-beaches/playas-principal-and-panteon
[2] http://www.moon.com/destinations/oaxaca/pacific-resorts/puerto-angel/sights-and-beaches/playa-zipolite
[3] http://www.moon.com/destinations/oaxaca/pacific-resorts/puerto-angel/sights-and-beaches/playas-san-agustinillo-and-mazunte