On Thursdays at 10:30 the La Jolla Library has Preschool Storytime. My daughter loves it. There is always some sort of small arts and crafts project she brings home too. She has actual preschool during this time now so we don't go anymore, but she enjoyed it from about 18 months onward.
Go to storytime and then head to Sammy's or the Museum of Contemporary Art Cafe for a kid friendly lunch that the entire family will enjoy!