San Juan is an agricultural town. Its major products are rice, corn and tobacco. The town has two major rivers: the Malanas River and Tineg River. These two rivers supply the townspeople with fish and they are also used to transport bamboo which is sold to resort owners in Vigan.

During the dry season, the townsfolk also plant string beans, eggplant, peanuts, bitter gourds, squashes, okra and tomatoes. Some also cultivate mangoes.