Maybe you should move, who wants their neighbors hearing every fart they make anyway. I would think that by now you would want to move based on the two neighbors being jerks and managment not caring. If it's not the vents, and you don't want to move, try laying some carpets down to absorb some of the noise, putting some thicker curtains on, or trying to fill up your apartment a little better. That should cut down on some of the noise. As for the shower, it is probably the vent that is allowing them to hear you.
What all are you blending?