First of all, congrats to all you guys for getting accepted to Penn. And we're all looking forward to meeting those of you that will be attending next year.
As far as housing is concerned, relax...you've still got some time. Most of the off campus housing search doesn't really begin until around February. The off campus housing office is great with helping you find a place, but make sure you check out the apt in person. West Philly is known to have some overpriced dumps....to say the least.
A lot of students choose to forego the off campus route the first year and live in Sansom grad housing or in the Dental House. For the most part, people in my class seem to be happy with both. But it really comes down to what the people living around you are like. I know that kids in the 2nd year hated those places.
Also, depending on your price range and whether you're looking to live in an apt complex, some good places that are pretty close to SDM include Chestnut Arms (41st & Chestnut), Chestnut Hall (39th & Chestnut), and Left Bank (31st &Walnut).
There are plenty of dental students in each building, and they provide a pretty wide range of cost. I live in Chestnut Hall and haven't had any complaints yet....it's also nice to live 1 block away from school.
hope that helps. there's a lot of Penn students roaming around on SDN, so I'm sure you'll get some other suggestions too.
good luck.