I work and live in Chino Hills and also have a preschooler. I asked around and got referrals from other parents as well as visited and interviewed 3 preschools before I made a decision. I am very happy with the school I chose. Let me know if you would like any recommendations.
The tiny tots program through the City of Chino Hills is a great option! Both of my kids went through it. I now have my daughter enrolled at the preschool at Good Earth Montessori on Chino Hills Parkway. I have heard some GREAT things about it! There is also a great program at Loving Savior..as I have heard :) Hope this helps!