I want to update, I had an interview this morning. I arrived 20 mins before schedule. Not many people there today. About 6-7 pp there, most of them came in pair or 3 pp per case, I guess. It's more than 30 pp the day I took biometric fingerprint. I wonder why it's so much different. Anyway, I waited about 25 minutes, then a nice lady said my name. I was led to her office. Before I had a seat, she asked me to raise my hand and do the oath thing. Of course, I said yes. First, she asked for my passport and DL. Then she asked me to tell her my name, address, dob, my parents' name. She asked the basic questions - like criminal, terrorist, arrest before?, etc. Then she asked for my I-20. I handed them to her. She asked me how many times I entered US and what was the first time I've been here. Then she asked for my original birth certificate, and I handed it to her. Then, she scanned through all document quickly. The rest was just chitchatting, like what I'm studying, when I'll be done, my summer in Central America.
Lastly, she said everything is all set and I should get GC in a month. She took I-94 and I-131 from me too. I forgot my EAD card at home (I just got it yesterday). She said not to worry, it'll be fine. However, she didn't stamp on my passport. I asked her about this. I told her that I want to update my information at school so that I can apply for jobs that are available for PR (since international students cannot drop resume online or set up for an interview). She said I should bring the letter from employer and bring here to approve. She might noticed that I was a bit worry about this, she told me that she'll send an approval for my case today, everything should be done in a week, then a welcome letter will be sent out in a week, and I can use the welcome letter as an evidence of GC. I have waited since April, so I think I can wait for another 2-3 weeks.
Then I thanked her, said good bye and have a nice day.
Total time in USCIS office today was less than 35-40 mins. When I got back to my car, parking meter had almost an hour left ^_^
A big thanks for everyone in this thread for helping me get through the whole process. Hope you all get interview soon and pass it easily.