mexican grocery in la area
Farm Fresh in Pasadena, Altadena and Hollywood is a good Mexican market. King Ranch at Huntington Drive and Magnolia in Monrovia is mostly Mexican plus multi-ethnic Latino, with deli items and prepared food in addition to its raw stuff. Gigante, at Azusa Rd. and Arrow Highway, is the same writ larger, if not necessarily better. The Food 4 Less store on Figueroa between Aves. 50 and 52 in Highland Park is to all intents and purposes a Latino market, and a pretty good one, especially in the meat department.
There are very very large mexican/latino grocery stores, as Dommy and Das note above, throughout most parts of Los Angeles. The largest of these have in-house bakeries, carnicerias, and tortillerias. At times there is a restaurant also that cooks good food for takeout. I like the variety of vegetables and herbs at unbeatable prices, the various cut to order meats (cortes al gusto), the cheese/dairy selection (try the crema or cotija cheese), the spices/marinades and the various drinks/juices/sodas you cant find anywhere else.
Secondly, there are smaller one-off smaller family run grocery stores throughout LA that might specialize in a region of mexico or other latin american country.
Lastly, there are many many food specialty shops in LA-carinicerias, panaderias and the like. I like Sonora bakery in East LA for the bread-especially the cheese (requeson/ricotta?)and jalapeno bread that sits on the counter as well as the teleras and pan bolillo (rolls, kinda). I also like Odonos carniceria.
With all the Mexicans and people of Mexican descent in Los Angeles, you bet your ombligo there's Mexican markets.
The ones I'm giving you are just the first ten I thought of within ten minutes' drive of my home in Valley Glen (we're not Van Nuys, we're not!):
Supermercado Vallarta, Victory and Ethel
Supermercado Vallarta, Vanowen and Woodman
Supermercado Vallarta, Vineland btw. Sherman and Vanowen
Carniceria Don Juan, Victory and Woodman
Carniceria Don Juan, Vanowen and Coldwater Canyon
El Super, Sherman Way and Bellaire (has Las Americas bakery)
Superior Warehouse, Lankershim near Oxnard
La Tapachulteca, Van Nuys near Victory
Valley Food Warehouse, Victory just east of Lankershim
Food Bag (actually Cuban), Victory and Tujunga