we're actually in St Lucia right now, although we are at Rodney Bay marina in the north of the island having our catamaran upgraded. We've been mostly kiting at Cas en Bas beach because it's closer but have gone down to Vieux Fort, where the Reef is, a couple of times.
It's a lovely spot - nice big beach, can get a bit crowded with swimmers though. In terms of kite sizes I don't know how much you weigh but think that you might not need the 9 ... The wind is 15-20 knots most days. Perhaps you would be better off bringing the 11 and a bigger kite.
Bring reef shoes and mosquito repellent! Let me know if you need any further info. Cheers
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