On Thursday, Friday and Saturday you can visit the farmers market in Liberia. This is a great experience for travelers because it allows them to see what fruits are in season. The sellers are also very friendly and offer you to try their produce. Specially if they see you are a tourist. Fruits and veggies aren't the only produce offered. There is cheese, fish and in some cases even medicinal plants.
Also and option after the market is stopping by the local butcher to purchase some chicharrones. These are fried pork rinds or meat, a typical snack through Costa Rica for parties and social gatherings. At this same location you can also purchase other goods (non-edibles).