Doesn't look like there's been much response to this one (!) so I'm going to use my contribution as my introduction to the forums, since I've just registered on the site.
I live in Zihuatanejo, Guerrero. My shopping is principally done at the local market--still one of those colorful, sometimes odoriferous and always fascinating warrens of human activity and commerce--or at the Comercial Mexicana supermarket.
I love the market and the streets behind it that that are filled with little shops bursting with piles of fresh produce and housewares, beans and dried chiles, and but tend to opt too often for the convenience of the Comercial Mexicana. Although during my first years here it wasn't easy to find a lot of variety in either fresh produce or packed goods, since the advent of the supermarkets about 10 years ago we have had access to an incredible selection. Of course there's always something that's missing. Years ago our unsatisfied cravings were for fresh lettuce, cranberry sauce, decent peanut butter and good crunchy dill pickles. Now things have changed and we're wishing for much more exotic fare such as quinoa, miso, Jewish rye bread and good, crunchy dill pickles! What is it with good crunchy dill pickles? They are just impossible to find.
Fish is definitely only worth buying at the local market or down at the fisherman's market on the beach, if you get there early enough in the day.
There are several stores around town (and also a stall in the market) selling the organic coffee from the hills of Guerrero. They also offer sea salt, agave nectar and vanilla from Veracruz. We go there, too.
We don't have any malls in this area, really. There are tourist centers--conglomerations of small shops and boutiques--in Ixtapa where you can buy T-shirts and pareos (sarongs) and bathing suits and jewellry, but they aren't really frequented by the locals.
Downtown Zihua has a number of walking streets with shops and restaurants, and the municipal government has recently revamped the whole core, constructing arches and arcades all along the streets of center town. So downtown Zihua is like one large, open-air mall, with protection from both sun and rain, but with a Mexican small-town feel. Much better than any modern, commercial shopping center, I'd say! (I have a blog entry or two at about how town looks these days, if anyone's interested.)