if its just one unit above you causing all the grief then either go and tell them if your people skills will result in s fisty cuff take it up with the building management, telling them its a noise problem and if the condensation tray is overflowing because of a blocked pipe a potential breeding ground for mozzies
If its just the rain then sponge/carpet is the way to go, and ask the landlord to try and fix it, if all goes horribly wrong ie the aircon falls out of the window then you can say its their fault for not fixing it.
Worth looking just above the unit as there is sometime a bit of space where it comes through the wall, normally just covered with a panel, you might be able to slide a carpet tile out, but make sure the fall is away from the house otherwise you have solve the noise but water will start to trickle in.
