Can I do my saliva test anywhere I want?
NO! First of all, spitting could conceivably transmit coronavirus, and second, it is really icky to do it in public. So please produce your saliva sample when you are alone in your own room at home or in your private office.
For everyone's sake, do not stand around producing your saliva sample in open spaces and common areas, at the test kit pick-up/drop-off sites, in public restrooms, on sidewalks, in a classroom, or in a shared office.