My 3 yr informal probation period started 7/9/15 and it will be over 7/9/18. I'm planning on going out of the country for 3 weeks, on 6/16/18 and will be returning around 7/7/18. I was also denied my citizenship last year because of the probation issue and the interviewer said he could not interview me for the citizenship until my probation period was over and that I would have to re-apply once it was over.
My green card is still valid and so I'm wondering if I would have any issues upon re-entering the country due to this situation?
You should not have a problem traveling abroad and returning to the US since you are a permanent resident and have a DUI conviction.