Should I Go To Trial?

I received a ticket for under age drinking on private property. During a BBQ on a quiet Sunday afternoon a next door neighbor called the police stating that there were under age kids drinking next door. This was a tactic to get the police to investigate because this neighbor didn't personally know any of these people so she had no way of knowing their actual ages. When the officer arrived she proceeded on to the property and asked if everyone was 21. The two that were not, one of which was myself admitted it and received tickets. Questions: 1. Since the neighbor did not know for sure about everyones ages did the officer have probable cause? 2. Did the officer trespass since it was private property and may not have had probable cause? 3. After the officer left it was noticed that she wrote the ticket for under age drinking on a public street. Is this enough of a defense to go to trial with or should I just plead guilty and be done with it? Thank you.