unpocorizado

I wrote an undergraduate thesis and my thesis advisor strongly suggested turning it into a journal article. He helped me pick a journal, but then gave me two options: 1) Publish it by myself and he wouldn't be part of the process (except for maybe slight edits) or 2) Collaborate with him and put him as a second author. He's leaving and taking a new position at a different school and I haven't done much with the material yet. Given the fact that my advisor is starting a new position and I've graduated, I envisioned doing all (or mostly all) of the revision work. Here's the tricky part: I emailed a POI recently at the program I really want to get into. I told her a bit about my research interests and she was really interested in my thesis and asked to see a copy of it. After reading it she told me she would be willing to help me explore publication options (I hadn't even mentioned that I was thinking about publishing it). I have NO IDEA about the proper protocol as far as my advisor goes. I feel like it would almost be cheating on him to work with this POI at this university, but I also know that my advisor is really busy and he admitted that it wasn't a good time to work extensively on an article with me. How should I proceed? I don't want to burn any bridges in academia so early by going to a different professor at a different university for help, but I also would like a chance to work with this POI. Or is it weird to work with a professor before even being admitted to the program? I'm new to this grad school thing and want to make sure I'm not totally naive going into this. Thanks so much for any help!

New to posting, but have been lurking for awhile. I'm applying for Spring 2012 admission (and Fall 2012 if I don't get into my top program) in urban planning. My top programs don't require the GRE if your GPA is above a 3.0. I graduated with a 3.5 from a top 20 liberal arts college and have done an internship in a planning consulting firm. I also have research experience (I'm in the process of publishing my undergrad thesis research as a first author) and I've been promised stellar LoRs. I have also identified professors in these programs whose work aligns with mine. However, since my GPA isn't that great, do you think I would benefit from taking the GRE or should I not even bother? If it would significantly enhance my application I will definitely do it, but I also don't want a bad score to have the opposite effect (I'm better at verbal than quant). Has anyone else had a similar experience? Thanks so much for any help!