A lady at one of the rental agencies advised that I stay farther from Place Catalogne and closer to the northwest section of the 15th. She didn't mention any specifics other than it was a nicer neighborhood and safer.

I'm still looking though, and am surprised at how much the agencies charge for a short rental. It's good to hear so many good things about the 15th though, I'm looking forward to being a resident in Paris even if it's only for a month and a half.