A disorderly ticket is a misdemeanor. Because the underlying charge invloves an "Offer to engage the services of a prostitute", there will be some problems with your green card status. A crime of this sort is looked at by INS as a crime involving Moral Turpitude and that is a potential ground for deportation.
You must fight the charge, not simply take care of it. You have a good defense since you never discussed money or sex. This sounds like it was a sting operation and unfortunately you got caught up in it. I would suggest you call the PA Bar Association and get a reccomendation for an attorney who locally handels these cases.
You need a lawyer.
Disorderly conduct may be a summary offense or a misdemeanor. In either case you should have a lawyer to try and keep this off your record. I have seen these sting operations but I have not seen them asking people to give up their right to trial. As to the immigration it would depend on the charges filed.
You absolutly need the services of an attorney. You would need both a Criminal Defense Attorney and an Immigration attorney. We have worked on several cases such as this with an immigration attorney and have found that a coordinated effort on the part of both attorneys is essential.
The situation that you described sounds exactly like the sting operations that law enforcement in the five county philadelphia area have been running for several years now. The fact that you signed papers waving your right to a trial is irrelevant. You cannot give up your right to trial at the time of your arrest. Even if you waived your preliminary hearing in front of a Magesterail District Justice without counsel you can still have the Prelimiary Hearing or a simlar hearing .
Remember the police are not looking out for your rights but an attorney will.
You should contact an attorney as soon as possible. Disorderly conduct can either be a misdemeanor or a summary offense. A summary offense is akin to a traffic ticket however it can still be considered a criminal conviction. You should take immediate action to protect your rights.