I was there 2 summers ago and had a great time - my last hoorah before my twins arrived). My wife and I stayed in San Pancho (also known as San Francisco) - 2km north of Sayulita at an awesome B&B -
http://www.casaobelisco.com/index.html - this was across the street from Costa Azul, which fpjb has already mentioned. If you're bringing significant others, this is a great house - awesome breakfast feasts and someone comes to the house every day around 2:00 for snacks (fajitas and quesadillas and excellent margaritas) while you're resting by the pool. 4 couples and I think you have the place to yourself.
The surf in Sayulita is a good longboard wave - nice long rides, but not much punch to the surf. I tend to look for a little more juice when I'm in Mexico, and there are boats in Sayulita that can take you around to various reefs in the Punta Mita area for $40 or so. Also, the beach break at San Pancho went off 2 days while I was there and we had some pretty heavy barrels right out front - I was told mid-August to September was the right time for the sandbars in San Pancho - this is also the hottest time of the year in Mex, but well worth it in my opinion.
Finally, there's a restaurant in San Pancho that's amazing - can't remember the name, but ask anyone about the steak in the piping hot bowl and they'll get you setup.
Enjoy...
Dave