The hidden message is

SHERLOCK I HAVE FOUND YOU

I didn't use the clue "where is it the pigs live?", but instead I use

!http://observeanalysededuce.files.wordpress.com/2010/08/pigpen.png If you click into the link above, you will see four different gird. And according the grid, we can find that different symbols(just like in the message) means different letter. So, if we follow the grids, we can find the hidden message.

The hidden message is:

SHERLOCK I HAVE FOUND YOU

I didn't use the clue "where is it the pigs live?", but instead I used:

http://observeanalysededuce.files.wordpress.com/2010/08/pigpen.png
If you click into the link above, you will see four different grids. And according to the grids, we can find that different symbols (just like in the message) mean different letters. So, if we follow the grids, we can find the hidden message.