Your boyfriend is free to travel. He should however, either notify the court that he wishes to have a court date after his return or hire an attorney that can request a court date after you both are back in New Jersey.
As far as how long he will lose his license your question is a bit premature. His case needs to be reviewed by a qualified attorney that understands the DUI laws of New Jersey.
Follow the instructions on the back of the summons to plead not guilty. Then go to court on the date that the court sets with a copy and an original of your drivers license. Speak with the prosecutor and offer him or her a copy of your drivers license and show her the original. Respectfully request that the prosecutor dismiss the summons and only have the court costs of $33 be imposed. This is in the discretion of the prosecutor.
In New York you can expect to be offered an ACD, which is an Adjournment in Contemplation of Dismissal, also known as a marijuana ACD. As a result of that you would not have a criminal record. You may have to do community service.
Be aware that you do not have to accept this offer, and you do have every right to challenge the proofs and assert your rights.
Make sure you have an experienced attorney analyze the facts and the law before accepting any plea.
It sounds like you have a court appointed attorney or you are represented by a public defender. You can ask the judge for a new attorney. You would have to convince the judge that your attorney is not properly representing you. This may be difficult, but you have a lot riding on the outcome of your case.
The other option is to retain a private attorney that has will devote the time necessary to your case.
From the information you have provided, specifically that your boyfriend is alleged to have been driving under the influence at the time that an accident took place and that there was serious injury, the county prosecutors office will conduct an investigation to determine whether to prosecute the case in Superior court as an indictable. If they do so as a third degree, depending on the physical condition of the victim and whether or not your boyfriend has a criminal record will depend on...
You should consider getting an attorney to contact the collection agency on your behalf to read and advise you regarding the civil demand.
Next, while you could have a public attorney represent you in the criminal court, you should consider having a consultation with a private attorney to help you decide if you would be better off fighting the case.