I'm at Vandy in the Latin American Studies MA program. Congrats on getting accepted; I'm jealous. I don't know the Africanist professor, but it's a great department overall. Anyways, I'd be happy to answer some of your questions as best I can.
1) My wife was 7 months pregnant when we moved to Nashville, so much of our free time revolves around our lovely daughter. It's worth it but I do miss going to rock shows. We've only been to a couple of venues, but just generally stay away from downtown clubs if you want to avoid pop country and butt rock. There are plenty of places with blues, country, or bluegrass open mics that would probably cater to your tastes, many in east Nashville. Also check out the Gulch... pretty trendy but some gems. Somebody else could probably tell you more. One more thing though, Vandy hosts an annual weekend music fest called Rites of Spring. Pretty eclectic mix from country to hip hop. They just announced some of the acts for this year; I'm looking forward to The National, Edward Sharpe and the Magnetic Zeroes, and Public Enemy. Here's the website: http://www.vanderbilt.edu/ros/ Check out the history tab for past lineups to give yourself an idea.
2) Undergrads generally have to live on campus so they tend to hang out at the places near Vandy. The undergrads that do go to the same places as the grads are generally pretty cool.
3) Nashville is not very bike friendly in most areas, but the buses do have bike racks on them and students ride for free. That way you can do a hybrid commute. Either way, you can get by without a car for a while.
4) Nashville is much more urban than I thought it would be. Granted, I spend most of my time in the Vandy bubble, but there doesn't seem to be the animosity that you'd expect. It's actually a pretty culturally diverse place... not as many people with southern drawls as we expected. My wife and I moved here from Paris so that was a bit different, but before that we lived in Milwaukee. We felt like Nashville is a southern Milwaukee (if that gives you any point of reference). They have similar demographics and they're both friendly, laid back, not too big but plenty to do, inexpensive. They are also both great drinking towns. The local brewery, Yazoo, has a new tasting room downtown that's pretty cool. You can get their beer all over town and it's delicious. Their old location on the north side is in a terrible are but the building is awesome and the Corsair Taproom that moved in is a great place. The Corner Pub near campus has a 50% off taps and rails happy hour from 3:00- 7:00 and they have decent bar food. My LAS cohort goes there every Friday for a Portuguese roundtable (which usually devolves into a mix of Portuguese, Spanish, and English) and a bunch of people from the history dept. go there for trivia. Also try Flying Saucer in the old train depot downtown. If you like beer, they have about a hundred on tap and they have good specials during the week.
http://www.yazoobrew.com/
http://corsairtaproom.com/
http://www.cornerpubtn.com/CP_midtown/index.html
http://www.beerknurd.com/stores/nashville/
5) There are tons of reasonably priced restaurants but no good pulled pork or Mexican. There is San Antonio Taco Company (SatCo.) which is mediocre Tex-Mex and a new BBQ place next to it, but I haven't heard anything good and it's always empty. For the best Mexican, stick to East Nashville. There are a ton of taco trucks and taquerias as well as my favorite Mexican place in town, La Hacienda. There are a lot of hole in the wall BBQ places but I haven't tried many of them. There is a Tennessee chain called Calhoun's which is pretty good and the Loveless Cafe is a can't miss place for southern cooking. They are known for their biscuits and smoked meats. It's about a 30 min. drive from the campus area and you'll have to wait as much as 2 hours to get a table if you go during a meal rush, but it's a Nashville staple and well worth the wait.
For places close to campus, you have to go the Pancake Pantry. Copy everything I said about The Loveless, but with pancakes. For more everyday places I like The Dog (hot dogs), and Mellow Mushroom (a pizza chain that I was not familiar with until moving here), Mediterranean Cuisine (home of Mediterranean cuisine and creative names).
http://www.lahaciendainc.com/
http://www.coppercellar.com/Restaurant-Calhouns.html
http://www.lovelesscafe.com/
http://www.thepancakepantry.com/
http://www.thedogofnashville.com/
http://www.mellowmushroom.com/locations#/store/index/nashville
I hope that helps.