You would not be subpoenaed to appear in court. As a party, you are expected to appear if you wish to contest the matter. When she files, you will be served with the Complaint and a summons requiring you to answer within 21 days. After service, the court will at some point, depending on the jurisdictions procedures, schedule a time for you (personally or through your attorney) to schedule a trial date. You will have your notice of the trial date through those means. IF you want a witness to appear on you behalf, you can issue a subpoena for that witness, but the court will not issue a subpoena for you.
You need to consult with a local family law atty.Every state has its own rules about how much time you have to file a response with the court after you have been served with papers. You should find out what you are looking at in terms of property division, custody, support, etc, as you may be able to negotiate a divorce agreement so that you wont have to fight in court.
Hearing dates are normally postponed for good cause. Again, you need to talk to a local atty who can advise you of what court dates are likely, how to get contuances, and perhaps you may hire someone so that you wont need to be present at every hearing.