On the first night, it looks like you should just go to Sala Rossa and stay. Nobunny is great live. Hunx & His Punx are fun, but Hunx loves getting naked, so, yeah, be prepared for that probably happening. Box Elders are also great. And Jay Reatard is also playing that night. Oh, and you might want to catch the Phenomenal Handclap Band early in the night if you want to dance.
The next night, the only can't-miss act there is Joel Plaskett & the Emergency. I think Joel is a really gifted and underrated songwriter. You might also want to check out the Butthole Surfers, if only because there's always a potential for a trainwreck. Maserati is also pretty good, but you wouldn't make it over to see Joel Plaskett in time. Mono's a pretty great Japanese band, but I would still see Joel Plaskett over Mono.
October 2nd: Yo La Tengo. Obviously. Maybe Soupjam, but you'd have to run from venue to venue to catch it. The Silent League has at least one member from Mercury Rev, and I like them a lot. And then you have to decide between Chain & the Gang and the Black Hollies.
Last day: Faust if you like Kraut rock, Os Mutantes if you like tropicalia, and the Fresh & Onlys if you like music.