Mexico is a big place facing two oceans. Any particular area you are thinking about? Cabo San Lucas, for example, is a long way away from the resorts in Cancun and Cozumel.
Lake Arenal in Costa Rica is a great place that time of year from what I understand (yes, not Mexico but "in the area" and very windsurfing-centric. Great surfing on the coasts)
Came across this while fact-checking my short post:
www.iwindsurf.com/travel.iws?genID=25