I have water pouring through the wall... in the bathroom into the tub, but outside through the wall as well. I was told by workers who are doing sewer work in the area, that it is the mixer valve. I couldn't see the item itself, the man told me to put my hand in there and feel it (I couldn't feel anything). He had cut a small area out of the siding and it exposed a portion of the pipes, but not the area that was actually leaking. Regardless, something serious is going on there, and I have had to turn the water off at the meter, since there is no other turn off between the house and there. I am really upset about this. Is there any way other than cutting out the whole portion off my house to see this? I have tried taking the shower handles off inside, but I can't really get anywhere with it. I also pulled one tile off and it exposed some disintegrating sheet rock behind it. Either way I try this, I fear it is going to be a huge mess. There is also evidence of water leaking up in the ceiling area, but until now, I had thought it was from an leak in the roof. I had to repair a spot near where it would have run down from. Now I see that was not it at all, or at least not all of it. What can I do? I wish I could just run away!

Before anything, the leak must be located and exposed. Until then you don't really know what you're dealing with. If you can't handle it then it's time to call in a plumber before any more damage occurs.
Good luck, Tom