You would enter a "Not Guilty" plea with the clerk of court within 30 days of the ticket. The clerk will set the hearing before a Hearing Officer or County Judge. If you desire to view the officer's notes regarding your ticket you will need to go to the clerk of court and ask to view the file. Inside, you will see the ticket and and any notes the officer made (i.e. Driver's attitude, statements, etc). The officer's statement regarding his observation is key to his case. Obviously, you will state you didn't run the stop sign. You will need to prepare; because you will need to see if the officer wrote the ticket correctly and if not, will those error(s) allow you to ask the Hearing Officer to dismiss the ticket.
You should definitely retain counsel on this. Depending on where your citation was and who your hearing is in front of, you may end up getting a raw deal. There are multiple different hearing officers in Pinellas county, whether you're north county or south county or over at night court at the real court house. . . each magistrate has a unique way of dealing with stop sign tickets- namely, that if it's your word against the officers, they'll basically always believe the officer. So I strongly recommend your defense include one or two additional witnesses. . . Just my honest practical experience watching pro se citation hearings in pinellas county. Sounds like you're doing your research and you're showing up prepared, and that's a great start. Best of luck to you.