are cooks allowed to whistle in the kitchen and while prepping food? I find it gross and unsanitary, what if they blow saliva onto my plate, based on food safety standards is this okay?
This question is better directed to your county's health department as restaurant hygiene is typically regulated at a local levels.
From what I can tell, there is no specific regulation prohibiting whistling in a commercial kitchen in the SF Bay Area counties of San Francisco, San Mateo and Santa Clara. I worked in a restaurant in SF County about 25 years ago and there was no prohibition back then and I doubt there is one today. I do not have personal experience with San Mateo nor Santa Clara Counties.
That said, there are far more worrisome restaurant worker behaviors (like not washing hands after using the lavatory, showing up to work sick, and improper food storage procedures) than whistling in a kitchen.
You have far bigger problems to worry about than kitchen workers whistling.
Heck, you may want to worry more about your fellow diners' hygiene issues as well.
Anyhow, that's the way I see it.
Best of luck.