As far as talking with AOG youth, I understand their ignorance, having come out of that church--but I also was able to find Orthodoxy by following the path the AOG showed me. So there's real promise with pentecostals, and I wouldn't give up on them just for that reason (if there are other reasons as well, then you may consider leaving).
In regards to the question about Mary Theotokos, remember that they have nothing against her; they merely misunderstand her position. For the ones who are just looking for a reaction, try to steer the conversation elsewhere. For the ones who are really seeking, try to put the issue into terms they can understand. For example, you may ask, "Do you worship the Apostle Paul because he spoke in tongues more than anyone else?" The answer is, "Of course not, but since he did, we should as well." There you have a talking point, and can show them something about the Church.