While most of the houses located in the 91789 zip code are in the City of Walnut. Not all houses in Walnut belong to the Walnut Valley Unified School District (some are in Rowland Unified). Also, some houses in the 91789 zip code are in Diamond Bar (south of 60 fwy). Here's the street listing link that identifies the assigned schools in Walnut.
Hope this helps. Feel free to contact if you need further assistance.
Jeff R. Lim
Realtor (22 yrs)
M J & L Realty Inc. Walnut, CA
DRE Lic # 01074730
Can you please provide and address or Trulia listing? You should work directly with an agent who can help you learn more about that specific property (and probably will know a lot about similar properties in the area). To find an agent, just click on the yellow button on the property's listing and you will be able to start a dialogue.
Please let me know if you have any questions or if I can help with anything else. I am happy to be a resource for you. Good luck with the search!
Ali, Trulia Voices Community Manager