I'm Lucy, and I'd be happy to answer your questions today.
1. You cannot be compelled to testify against yourself. It doesn't even make sense for the district attorney to subpoena you, unless they're asking you to produce documents. The privilege against self-incrimination does not extend to producing documentary evidence.
2. The Fifth Amendment provides protection here. It's possible to file a Motion to Quash. However, as a practical matter, what the subpoena is really doing is compelling you to attend the trial. If you're not there, you'll automatically lose the case, so it's in your best interests to show up. And you can object at the time if the D.A. tries to call you as a witness. You have an absolute privilege NOT to incriminate yourself, even when acting as your own attorney. However, you should know that if you CHOOSE to take the stand, they can ask you any questions they want. So, if you're planning to tell the judge your side of the story as part of the speeding ticket trial (which you also don't need to do), there's no reason to move to quash the subpoena.
What I would probably do in this situation is call the DA and ask if the subpoena was issued by mistake. But you can choose to file a Motion to Quash.
It's important that you are 100% satisfied with my courtesy and professionalism. Thank you.