US agents for Mexican underwriters are called SURPLUS LINE BROKERS. Lewis & Lewis has the tightest relationship with a parent underwriter in the Surplus Line Broker industry (Qualitas in Tijuana). Enough of that, I want to move on and help the OP...
For serious grocery shopping, I would skip trying to do anything in Tijuana or Ensenada. Parking sucks, and is impossible with an RV rig. Since you are prohibited from entering Mexico with eat, eggs, fresh milk, fruit and vegetables, you need to gear up down here and here's a suggestion.
105 miles south of Ensenada is the San Quintin Valley, the towns of Colonia Vicente Guerrero, San Quintin, and Lazaro Cardenas.
You will travel endless curves and grades south of Ensenada and pass through 4 medium size villages. Then the road doglegs to the right, then left again paralleling the coast. About TEN MILES down the straight but rolling highway your co-pilot will have to keep a sharp eye out on the right hand side.
There you will encounter a large Shamrock Green with yellow trim building about 150' off the highway.
BODEGA AURRERA
Bodega Aurrera stores are part of the Sam's Club, Wal-Mart chain. This one requires no membership.
Inside you will find excellent shopping for familiar items. Fresh milk in plastic jugs tastes indistinguishable from US milk. San Quintin is a major exporter of fruits and vegetables and it is doubtful anything you bring from home would hold a candle to this stuff. I just shopped at this store four hours ago. You need to bring your condiments (catchup and apple sauce), and spices from home. Like anywhere else in Mexico you will have to park outside the parking lot which I swear they are all perfect for 10 foot long cars. There are no inspection stations between the border and BdeLA. Get charcoal briquets there if you need them. Eggs too. The produce is as safe as anything in the states. Wait till just get a load of the produce prices! Especially avacados
Same exact products, Bodega Aurrera is SIGNIFICANTLY LESS EXPENSIVE than Sam's Club or Wal-Mart Mexico. I just shopped all three.
You can one-stop gear-up for BdeLA here.
I'm in El Rosario and will be working on the Halcones del Desierto fire engine and ambulance electrical tomorrow. Converting everything to LED strobe emergency lights. The Pemex gasolinera here is the last one and it's a long way from there to the bay. Antonio's pumps are dead on correct, a rarity in Mexico.
Halcones del Desierto has ambulance service as far south as Catavina. Servicio Telefonica Rural is located along Mex 1 at various ranchos.
And EVERYONE! PLEASE! If you drive through El Rosario, stop at the Pemex gasolinera. Halcones del Desierto is being operated out of Antonio's pocket. It is a registered non profit organization. The man is dead-honest and every donated centavo and cent goes into the 2 machines. I donate time, labor, and LED lights to the service. Help Save Your Own Life. You know how utterly desolate that 77 mile stretch of highway is between El Rosario and Catavina. Many ambulance services and donation collections are flaky in Mexico. This isn't one of them. Go to the CASHIER WINDOW and say the magic word DONATION. Then take a moment and admire the machines parked next door. Volunteers are EMT trained. The lighting, all of it on both machines, is my contribution. Antonio has been a friend for many long years. He speaks English. Thank You.