I am trying to find out who owns a specific piece of property in gilroy California.
How can I attain that information?

In some counties in California this info may be available from the register of deed for that county. But often it may also be not up to date either.
Your best method go down to the register of deed and they will tell you, or you can look up who is listed on the deed and if there are any liens or mortages.

Then you can go to the tax office and see who and where the bill is being sent on that property