It is unlikely you will encounter bears in your neighborhood. The California Black Bear is an extremely timid creature and will usually run at the sign of a person. If you do see a bear in your neighborhood, contact your local police department and the Los Angeles County Department of Animal Care & Control at (626) 962-3577.
Bears are attracted to any type of food left outdoors, especially at night and in some cases, bird feeders.
You can prevent them from coming near your property by storing all food indoors and all trash in airtight garbage cans.