If it's just this package that you can't get to install, you could download the tarball manually, and then use pip to install it from that file. The Django download site has checksums that you can validate manually as well. I don't use osx, but probably something like this would help:
cd /tmp
wget https://pypi.python.org/packages/source/D/Django/Django-1.5.1.tar.gz
md5sum Django-1.5.1.tar.gz
pip install Django-1.5.1.tar.gz