These are the popular grocery stores in Playa del Carmen; Sam's Club, Wal-Mart, Maga and Soronia.

I prefer Soronia (a good Mexican grocery store) or Mega to Wal-Mart, because during the high season Wal-Mart is the busiest place in Playa del Carmen, besides the beach! Soronia also carries more American brands (not a lot but more than some other Mexican Grocery Stores), I also like it because It's right on the highway so I miss the traffic in town and while I'm at Soronia it's easy to us the turnaround on the highway and hit Sam's Club on they way back to the villas.

In Cancan there is a great grocery Store called "Superama" it's a Wal-Mart but only has food (nice produce), and in the same complex is another Sam's Club. Sometimes it's easier to get to Superama in Cancun than to the stores in Playa del Carmen especially if you are staying in the villas  MexicoVacationVillas.com offers. It's located right on the main highway 307 about 5 miles north of the airport turn-off. Since it's right on the main highway it's easy to find. I'd Pass on eating at the the restaurant "VIP's" it's like a "Denny's" in the states, my option is that Mexican restaurant chains are not usually up to par, but that is me.

The Costco is in Cancun.