Well, to answer my own question: I gave up on kitesurfchina.com. Never did get a response from them. No idea if they are still a going concern or not. So, I went for plan B - I just showed up in Bo'ao (supposedly the prime kitesurfing spot on Hainan Island) and hoped for the best.
I walked to the beach and saw some kites way off in the distance. About 20 minutes walking in the blistering heat bought me to the first spot. Maybe about half a dozen locals out kiting. Seemed reasonably windy but my heart sank a bit when I saw people mainly riding foils. But there were a few TTs and SBs and therefore hope. On that section of the beach, they all told me more or less the same story. Everyone had their own gear and that there were no places to rent or take lessons. Thank goodness for translation APPs since all but one kiter was Chinese and their English was about the level of my Chinese - almost non-existent. The one exception was a Russian with good English but he too was adamant that there were no schools or rentals. Not enough patronage to make a school viable he said.
Undeterred, I kept walking up the beach for about another 20 minutes (it is a big beach !) to the second set of kites. Jackpot
. I found a small school located right on the beach that I could rent from (and sell me a pair of board shorts because I didn't bring any gear with me because I am travelling as light as possible).
. Kitesurfed in China. How many other people can say that ?
I had a great session. They had a compressor a with hose running down to the beach. Kites were all pumped up and rigged by the staff and ready to go right off the beach. Water was warm, no wetsuit required. It was strange to see most of the locals wearing full wetsuits and face masks like ski masks. But, I think that this was more for sun protection than for warmth. The surf was small which suited me just fine under the circumstances. Wind strength - 12 m was a bit big. 9 m was a bit small and I am a real light weight, under 60 kg. Don't know what other days would be like but I get the impression it is not a high wind spot, at least at this time of the year.
Location: GPS coordinates somewhere around 19.181886, 110.595907 ~ 19.182575, 110.592679 will get you close to the school. If you find a sign saying Baron Mansion from the beach side, or see a large statue of four golden horses and a chariot with a Roman goddess from the road side, then you are right on it.