You have an advantage there already; if these guys are partying on a regular basis until 4 am, its very likely that they sleep in late.
Now, if the rules are the same in the UK then here or similar, you can get busted for noise disturbance between 11 pm and 7 am (if Im not mistaken)
If you set the mp3 player to blast its music between 8 am and noon, you're probably nail them right when their in the middle of their 'night' and wont be caught because you are in right to do so in these hours. Still. I'd suggest you play a tape of hammers and chainsaw so they think you're just renovating in there... even better
