Hello Steve,
Availability can vary, with 4-5 (or more) US or regional brands usually on the supermarket shelves. It seems to me that Science Diet and Purina are always obtainable.
There are plenty of good local vets (sometimes they will sell different brands of pet foods as well), if you want recommendations for the Coronado area you can likely find some via the most popular beach community website in English: http://www.playacommunity.com/.
Hope this helps!