Running a pre-release of course is going to have its problems. First thing first is an `lspci` and confirm if you're stuck with a broadcom wifi chipset. I'm actually surprised the "quality" hardware in the Mac would even have such a chipset.
I'm curious as to how a 13.04 *buntu release fares in the same hardware, perhaps trying a daily with updates rolled in to the disc. If I had money to burn, I'd replace OS X on it just to stick it to Mac folks, ah sadism.