There is no public defender for PA ticket hearings. You go to a district magistrate and its you, the DM and the officer in a hearing.
There is instructions right on the ticket with your options. You can plead not guilty and take the ticket directly to the DM if you want, but like I said, you will have to wait for a hearing to be scheduled to even get an answer. IMO its not worth the hassle. Pay the ticket and take it as a lesson learned.
Honestly, I have been pulled over with dead inspection 3 times. All three times were 100% my fault, all three times I corrected it immediately, but all three times I paid the fine because it was a no points ticket.
The only time you should ever plead not guilty and try to plead it down is if you get a points ticket.