While I was in Panama over this past weekend (along with spending the day in NYC and a long layover in Miami), I had a chance to go to a few grocery stores, ranging from a tiny corner store to a big, air conditioned, modern supermarket and while a lot of what's in the big market is already Westernized (and particularly Americanized in the case of Panama), it's still an interesting look into how the locals really live.
Then I remembered I also enjoyed going to grocery stores in other countries.
One note is that at the supermarket, there was a security guard who was totally eyeballing us and following us (me and my girlfriend) around the store. The thing is it was like he was almost trying to be as conspicuous about it as possible. But again, that is part of the cultural difference that makes things interesting. I have to say their bathroom was spotlessly clean.
But in summary, visiting a grocery store is a good way to get a look into the local culture. And a good way to pick up local snacks to bring back as souvenirs.