My kids walked over to the kite surfing school just past the Marriott in July. They offer 5 hours of lessons before you can go out by yourself. I didn't get the cost as my kids were not interested in investing 5 hours as we were leaving a few days later. Go there early in your trip if you're interested.
I would not recommend kite surfing for beginners in Aruba. The winds blow offshore which is not ideal for learning. I would take lessons prior to going if where you live has conditions favorable for kite surfing.