Congratulations on the acceptance!!
I cannot speak of your dept as I come from another faculty, but UMN territories on both Minneapolis and St Paul are awesome. Although I visited the campus during one of the gloomiest weeks of January, I liked it a lot. The atmosphere was humid, and will surely be more humid during the spring and summer months. People in my dept (profs, staff, grad students) were very nice, and I don't think it is otherwise in yours. The cities around the campuses are heavily student-oriented (sports bars, restaurants, art shops, and so on), which is a huge plus in such a big metropolis. Downtown is merely 10 minutes away from the campuses. Public transportation is fantastic, and covers almost all areas where students live. I've heard a new lightrail is being built at the moment, which when done, will add more ease to commuters. Also, almost everyone rides bicycles - I myself am buying a couple (one mountain, one road) before I head out. Apparently, twin cities is the best city in the US for riding bikes, according to the Bicycling magazine, and it certainly seems to be true.
For more, feel free to browse through or ask questions in the following threads:
Hope this helps!