My vote is for the north end of Playa.
Many gorgeous condos to choose from.
The BEST beaches in the area.
Lots to do in the evening in walking distance, yet the far north end is quiet at night for sleeping (at least where we stayed, Arena Blanca condos on Calle 38).
Easy walk to downtown, lots of great restaurants nearby, and Mega and Wal Mart in walking distance (although laden with bags you will want to cab it back, not a problem)
Also an easy walk to the bus station or colectivo street, to do day trips.