There's a Walmart, a Costco, and a Sam's Club for food here in Puerto Vallarta. I can get by with buying food between 500 Mexican pesos and 1,000 pesos (US $27 to $55) a month. Those are tourist places so it's a little more expensive to buy food in these places than in non-tourist stores. For example, if you go to the open air markets that are mainly used by the Mexican nationals, you can buy food for a lot less. One of my co-workers spends 200 pesos to 300 pesos ($11 to $16) for himself every couple of weeks on food that he eats at home.
Food costs in the Walmarts and Sam's Clubs in Puerto Vallarta are very similar to prices generally in the States, which comes as a surprise to a lot of people that move down here to Mexico. They think they're going to Mexico and everything's going to be so much cheaper. It's more than just food. It was really a wake up call for me that some things are pretty similar in price in Mexico compared to what they are up in the States. Food purchased in places like Walmart and Sam’s Clubs is one of them. Electronics is another one.
Some of the open air markets in Puerto Vallarta are in little corner stores and little buildings, and some of them are just booths. They're even selling out of their vans or their cars all kinds fruits, breads, meat, cheese, or tortillas. You can go to the open air market and get pretty much anything that you want. Anything you buy in an open air market will be a lot cheaper, but it will all be naturally grown products. It won't be brand-named things that you would find in Walmart.
In terms of price, a gallon of milk may be 20 pesos ($1). For fruit, you buy by the kilo (2.2 pounds), and it depends on the fruit that you're buying, but the price could be 25 pesos to 75 pesos per kilo ($0.77 to $1.86 per pound) of fruit. A kilo of tortillas is 10 pesos ($0.25 per pound). It's pretty much the cheapest thing that you can find in Mexico. Eggs in the open air market are priced pretty similar to what they are in Walmart. Bread is pretty cheap. You don't really get it by the loaf. You just get it in a big roll like a roll for a sandwich, but five times bigger, which costs 20 pesos to 30 pesos ($1 to $1.50). It's all pretty cheap.
You can go to the open air markets for the fruits, vegetables, bread, and other stuff and then go to Walmart for coffee, meat, chips, juice, and similar items.
Overall, the cost of food in Puerto Vallarta compared to the US definitely saves you some money. In Puerto Vallarta, I'm spending 500 pesos to 600 pesos ($27 to $33). That's less than $50. So yes, you definitely save a decent amount of money.
(Mexican spicy beer cocktail with shrimp, pictured. Also known as Michelada con camarones-- Michelada with shrimp)