That area was somewhat dicey when I took classes at Temple years ago, but the campus felt safe. I didn’t ever venture there after dark, however.
I lived in Center City as did a few of my classmates and if you used common sense, that area was pretty decent and fun back then.
From what I understand, even Center City Philadelphia is not the safest place to roam around in anymore, especially at night. I don't know if in your Temple days you ever got up to the Kensington Avenue area, right near the Frankford El, which has been mentioned a few times already on this thread, but at one time that was a much safer and cleaner neighborhood too, filled with working people and their families, and small businesses. But that has degenerated into a filthy, disgusting, open drug-selling and prostitution neighborhood, filled with people living out on the street, and they call it a "bust-free-zone", as the Philadelphia police don't bother them there.
I posted this youtube link on another thread recently, but if you haven't seen it, and you're interested, there are a lot of youtube video links at this youtube search link that show what a mess that area has become. If you haven't seen that area of Philly (and if you have the stomach for it), you might want to take a look at a couple of those videos, but I'll warn you first that they are heart-wrenching, sickening, and depressing. Here's that youtube search link:
"Kensington Ave Philadelphia"