Legal Question in Criminal Law in California

May be able to but if the subpoena process is being used to harass, it will cause issues. The person who receives a subpoena must be able to provide evidence that is relevant to case at hand, so practically sepaking you wont subpoena all these people

The answer is, probably, yes but why. You only want to subpoena those witnesses that can help you--not those who's testimony will hurt you.

You can try, but be prepared to deal with and oppose Protective Motions brought by the prosecutor in response. Then the judge will consider your legal arguments and Points and Authorities to make a decision on who would be actually relevant to your defense. You won't be allowed to use subpoena power simply to harass people or the prosecutor. Remember also, you have to pay subpoena and witness fees for any govt agent you do this to.