For windsurfing in Istria most windsurfers go to spots south of Pula, Medulin, Premantura, Pomer. You can check spots on this link:
You can see weather for this spot on this link:
If you are from western part of Austria you can go trough Slovenia, Ljubljana Postojna Reka Učka Pula. If you are from eastern part of Austria you can go trough Hungary in this case you dont have to pay for highway sticker trough Slovenia, but you have to pay for Hungary and Croatia. Travel costs in both cases are approximately the same.
Do you now any spots in Austria for snowkiting. For example is it possible to snowkite on Saualpen.