The Best Beach in Mexico: Tulum is a 90 minute drive south of Cancun. Awesome restaurants (both in town and at the beach), small boutique hotels steps from the water, and just over-all wonderful atmosphere. Be sure to rent bikes to get around the town, the beach, or between the two.
Sayulita is a fantastic and fun beach town. Relaxed surfer vibe (and a great place to take surf lessons), good restaurants, and a handful of cool bars. But be warned: Sayulita has become super popular over the last decade and the town can get very busy.
Isla’s North Beach is the best kid-friendly beach in Mexico. The town is walkable and relaxed and feels close to idyllic. The downside? Almost no local culture and the atmosphere is a little on the lame side. Oh, and you really have to hunt (and get out of the main town) to find good Mexican food.