Area to avoid in South Bay Area?

Relocating to Bay Area soon.
What are some areas that I should avoid when searching for home?
For example,
I don’t want to love in a loud area where mostly college grads and singles live.
Any park where there are many homeless people?
An area where crimes are frequent?
Basically, I am looking for sketchy areas to avoid.

I am looking mainly San Mateo, Palo Alto, Menlo Park, Los Altos, Saratoga, Cupertino, Sunnyvale

Thanks

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