Playa / Main Beach
If you want to spend as much time as possible sunbathing and swimming, obviously you'll want to stay near the main beach (the playa--not to be confused with the little playita near the town pier). And if you absolutely must swim in a pool, the Hotel Lagunita has a small pool available for its guests, one of only two pools we know of in Yelapa.
Rentals right on the main beach tend to be smaller and less private than those further away, so if you don't mind walking a bit to get to the water, we'd recommend looking somewhere else.
Beach rentals are listed as area number 3.5 and 4 on the new spreadsheet (go here and select "File >> Download as >>" to download your own copy). Note that walking distance between the beach and other areas in Yelapa depends on whether the mouth of the river can be walked across as a short cut.