Search the Web. A large variety of food is grown and processed locally throughout the year. Domestically raised food is cheap compared to other countries. There are also imported foods available from neighboring countries and the west. Canned goods are relatively cheap, but things like imported cheese and meat are costly.
Basic food is cheapest and often of the best quality in markets.
These correspond to what Americans call Farmers' Markets. Rice costs approximately 11.50 pesos per kilo, pork is about 60 pesos, chicken 60, and beef 80. The price of fish and seafood is very inconsistent. As long as the weather is good prices may be as low as 18 pesos a kilo for fish, but when there has been a typhoon, or just bad weather, the price may double or triple. In comparison to meat and fish, vegetables generally are not cheap.