It is suggested that you purchase the bulk of your groceries prior to arriving in Mexico.  Food prices in our area are more expensive and
the selection is less.  Things like milk, bread and fruit can be purchased in Mexico if you don't want to stalk up on them.  They will be a
little more expense, but they are readily available.  As mentioned, other groceries are available in Mexico, they will just cost a little more
and the selection will be less.  The exception would be fruit as there is often varieties in season that are cheaper and really tasty.

One of the great options for grocery shopping in San Diego is Food 4 Less Grocery Stores.  Here's a link to help you with directions:
http://local.yahoo.com/info-20774273-food-4-less-chula-vista?csz=San+Diego%2C+CA

If the above link fails to work (sometimes they change things a bit, just google Food 4 Less stores in San Diego and choose the one
located off Palomar St.  It's located just off the I-5 freeway and is the easiest to get to on your way from San Diego to the border.

Food 4 Less
(619) 498-0327
660 Palomar St, Chula Vista, CA 91911

Another option that a few groups have used, is to buy your groceries via Costo or Sams Club.  You can place your order ahead of time,
they'll gather everything together for you, and you just review your purchase and pick it up.  You can do a Google search for these stores
in the San Diego area if you'd like.

Here's a helpful hint; It's best to choose grocery stores located in Chula Vista, or National City, as they are located between San Diego
and the border.  They are easier to find your way around in and are located just off freeways I-5 and 805 (the two freeways that go from
San Diego to the border).
Go Missions to Mexico
Grocery Shopping in San Diego