You raise several issues.
1. If you have no money the court may appoint you an attorney. However, some courts will require your parents to pay for your attorney since you are under 21 and in NY parents are required to support their children until 21.
2. You should not plead guilty without an attorney representing you since you are charged with a misdemeanor. Since you are under 19 and this is your first arrest if you are convicted of a misdemeanor you must receive a youthful offender adjudication so you will not have a criminal conviction. The maximum sentence is 6 months in sale, but based upon your lack of a previous record you are not likely to receive a jail sentence if convicted.
4. The faiilure of the police to read you Miranda rights only comes into play if you gave a statement.
5. The best way to get an ACD is to get an attorney who is experienced in the area where your case is pending.
Taking your questions in the order you asked them, Miranda warnings only affect the admissibility of any statements (confessions, admissions, etc.) the government intends to offer as evidence against you. If there are no such statements, then the fact that you were never read your right doesn't affect anything. An ACD is a common disposition in these types of cases, but you really need to consult with an attorney familiar with the specific facts of your case and local practice to make an informed decision as to whether accepting an ACD is you best way out. As the Miranda rights state, if you can not afford a lawyer, you have the right to have the court appoint you a lawyer, so if you have no money, you can ask the judge to give you a free lawyer. The maximum fine for a misdemeanor is $1,000. There are also mandatory court surcharges of $200. An ACD carries no fines or surcharges but the Court can impose other conditions such as attendance at a program. The last two questions are impossible to answer without knowing more facts about the case, you background, and the particular workings of the court you are in. Good luck.
The court will have an attorney there for those who can not afford to have private counsel, as they are legally required to do... If you have no priors the offer usualy is an ACD, but this may vary by county and some counties require a stop shoplifting class or community service...
Ask for the court to assign an attorney. DO NOT PLEAD GUILTY TO THIS CHARGE! You cannot receive a record if you are 18. Tell the Court you cannot afford an attorney and ask for Legal Aid!
I am a criminal defense attorney practicing in Nassau, Suffolk and New York City. The above information is not a substitution for a meeting whereas all potential legal issues can be discussed.