In Valencia town every Sunday Flea Market(Valencia Plaza)from 6am till noon you can find good fruit trees from 40pesos-250pesos. And if you like to roam around the town you can find cheaper fruit trees, the Valencia Department of Agriculture also can help you for more resources. And "Gloria Farm"-300meter from town plaza sells a good variety but pricey.
I bought most of my fruit trees in Apolong-a village after the Forest Camp they have more varieties and very good price.