How long to process AP? Travel with stamp in lieu of GC?

[myjwb 0]

I posted elsewhere questions about whether we should apply for AP at this point, since our interview for AOS is scheduled for June 7, 2010. We want to travel in late July or early August. Folks in the other forum thought they would probably not process our AP since it is so close to our interview date. So I am thinking of waiting to see the outcome of the interview. If all goes well with that, I suppose we would probably have the green card before traveling. But if there is some delay (e.g., they need more documents, or whatever they might come up with), then we could apply for AP right after we are aware of the delay. SO I am wondering how long it is really taking them to process AP for someone with an I-485 in process?

If we are approved in time for travel but don't have the physical card, I'm assuming we can at least get the stamp in the passport at our local office via an INFOPASS appt. But can anyone tell me for sure whether that stamp is sufficient to travel outside the US? I.e., is it sufficient to re-enter, and also to get out of the country you are visiting (in this case Turkey)?