The only PATH turnstiles that are bike friendly are the larger handicap ones. I think they are only at the 33rd, Hoboken, Pavonia, Journal Square and possibly Newark stops.Those turnstiles do not use turnstiles, instead they open inward so a wheelchair can get through. That works well for a bicycle as well. When exiting Hoboken at rush hour I recommend exiting from the front of the train closest to the NJ transit train station. Once past the PATH train exit up the steep steps and not the long hallway. The steps are steeper, but less crowded. Once on ground level you can double back toward the train station. From 6:30am to 9:30am or so and 3:30pm to 6:30pm you have to have your bike folded. I see people at those times still come on with unfoldable bikes. Yesterday I happened to be on the PATH at 4pm and did not fold it. Nobody bothered me and the train to Hoboken was not crowded. Closer to normal rush hour the bike rules might be enforced more. I generally commute on the off hours so I never fold my bike when in the PATH. I generally stand next to the middle pole and move the bike to accomodate people exiting/entering on open doors. I also take advantage of the empty wheelchair area which normally fits two seats that are removed to accomodate a wheelchair. With your back to the wall and your front tire near the sliding doors there is still plenty of room for people to enter and exit the train.
As for the magnet situation, my MuXl stays in place when folded. The rear rack on my MuXl might make a difference as well since I carry it from there when not using the El Boso. I have the airzound horn on my handlebars. It is positioned so I can still fold the bike and have access to the horn when riding without moving the horn.