March is the trough. The North Pacific winter is winding down so Nayarit's swell becomes occasional, and the Southern Ocean has not yet started producing the south swell that Oaxaca lives on. For a few weeks neither coast has a season.
That does not mean nothing works. The Nayarit points are very consistent and still pick up what arrives; it just arrives less often. What March asks for is flexibility about which day rather than which coast, which is the opposite of the rest of the year here.
The water at Sayulita is at its floor of 24°C and Puerto Escondido is at 28°C, the widest the gap gets all year. In practical terms the north coast in March is the one month of twelve where somebody might want a shorty in Mexico.
