The wind at Guincho can become realy strong, that means around 30 knots and more. There are some days with less wind of course . The waves can be around 2 meters.
There is also a nice current in direction to the rocks, so if you drop your kite be quick.
If you are lucky you will have some moderate days with winds around 20 knots and little waves. It's just a question of luck.
Take a look at the photos to have an idea.
In my opinion you will find better / more secure places to kitesurf in Portugal.
Enjoy your stage