Be advised that Mexican mattresses are not sized the same as US /CDN standards. To make sure your mattress is sized for your bed (and sheet sets), check the actual dimensions printed on the items. Friends have bought king mattresses at Costco in Hermosillo only to discover too late that they were Mexican sized (shorter and wider).
Ashley in Hermosillo also carries US /CDN sizes. Ashely will deliver to San Carlos for a fee, but you can’t take anything home from the store — you have to wait about one month for the order to arrive from California.
Sears has a large selection of mattresses, many of them Sealy. Casa Bonita, Costco, Sam’s Club, Coppel, and Walmart all also carry mattresses