Put the wifi on 5GHz so it is not on the same band as bluetooth and everything else. The 2.4GHz band is simply overcrowded and thus very very noisy causing all sorts of trouble. For some that means not being able to use the wifi when bluetooth is turned on. Is not an Apple problem, any other brand has the same issue with some of their products. It also doesn't matter if you use OS X, Windows, Linux or something else.