when i was an undergrad i helped at two other schools, one that wanted us to let the PNMs know we came from another chapter, and another that didn't want it mentioned. it was much better to be open about it, especially since at the school where we didn't mention it i got into some interesting conversations about what dorm i had lived in the previous years with some PNMs. oh, and not to mention i ended up rushing a girl from my high school who knew i did not go to her school.
either way, i would do some research on the school and greek life there, it'll help facilitate easier conversations!