Well, let's find out ;) Move your numpy download somewhere like ~/numpy-1.5.1, then do

cd numpy-1.5.1
python3.1 setup.py build
sudo python3.1 setup.py install

You should probably also do

sudo rm -rf  /usr/local/lib/python3.1/site-packages/numpy-1.5.1 before the build as well as remove your local build directory. You might also need to change ownership of the files from root to yourself.

Chuck