North part of the island is completely different from the south part. The path from the ocean to the top of Pico de Teide is about half shorter and therefore steeper. The coast is lined with steep cliffs that make the access harder for the water. But at some points the cliffs open and you can find a beautiful sandy beaches. Good examples are Almacíga, Bajamar, Los Patos and Playa del Socorro.
With an extremely indented coastline, every direction of the wind is very gusty, and it also rises with the cliffs so the wind does not come to the beach. Officially there are not any WS or Kite spots on the north. Local WS riders (Dany Bruch, Alex Mussolini) have surfed few times in the past in the surroundings of La Caleta de Interian and Punta del Hidalgo. But jet skis that helped them out before they ended close to the cliffs accompanied them. You can find a video from one session here. Waves are for most of the year bigger and harsher than on the south. On most places the waves hit the cliffs and after that creates a strong currents that head back to the ocean. Anyway the conditions are not that wild on the spots mentioned above and there are good waves for surfing for both beginners and advanced riders. It just depends on the size of the swell. During the winter waves can be really big. If you are lucky you can see an amazing show thanks to the local surfers and jet skis. You can watch the video here.
In a summary, the north of the island is not the best for windsurfing and kitesurfing. This part of the island is better for trekking, surfing or visiting the local Guachinche (traditional local restaurant with the true Tenerife spirit) :-).