Mount them in the re-bumper if you have that, or you can mount one beside the windshield washer resevoir on the passenger side, and the opposite side on the driver's side.
I personally would stay away from mounting ballasts on the bumper cover or anything else that moves while you're driving. Mounting them on a solid part of the car, preferably metal, is safer.
Are there any places that we shouldn't mount them? I've read that on some cars there are problems with the ballasts "not getting along" with other electrical things in the car when mounted too close to them. Just thought I would check if this is an issue with 6th gen accords.
There won't be any electrical interference no matter where you put them. But you don't want to mount them on anything that gets warm/hot, moves around while driving, or anything that won't provide good adhesion.