I posted a question before regarding this subject, and read other ones posted before, but none has successfully solved my problem.
I am trying to install PIL on Mac
In our virtualenv we found all we needed to do was:
pip uninstall PIL
brew install libjpeg
pip install PIL
which is simpler than some of the above and may be enough for others with this problem too. Although there was an xcode warning on the brew and a setup.py package warning on the reinstall of PIL, all the tests that previously failed with jpeg decode errors successfully ran after just the quick action above.