Let me give you some other ideas. My in-laws went to Puerto Escondido as a side trip from Oaxaca and liked it. We also have some friends who may be moving to Progreso, which is on the beach not far from merida and they like it a lot. I haven't been to these yet, but maybe next year. Also, many people here (in San Miguel) go to the beach in Sayulita and San Francisco (San Pancho), which are about an hour's drive north of Puerto Vallarta. The Four Seasons just built a large resort at Punta de Mita, so the highways are suddenly much better. For some other ideas, as well as homes to rent, you might want to look at http://www.vrbo.com (Vacation Rentals by Owner).
Ed San Miguel