Ask the court for a public defender if you can't afford an attorney. Ensure that he puts your friends that were with you on the witness list. It might be too late to get video from where you were with them, but it might not hurt to try. IF you can prove that the little old lady

While you don't want the post office involved, your attorney (if they have the time) can see if she had ever reported similar crimes to the post office. If so, and if you can prove you were not in the area during the times of those crimes, you might be able to beat this one.

...nothing against PDs, but you might be able to spend some money and get an attorney with less of a caseload. PDs are pretty busy and you might just be another statistic.