I want to start developing for it. I could
pip install but I'd prefer a proper repo.
Is there a PPA that's up to date?
Django 1.2 is included in Maverick Meerkat (still under development), but it appears that an unofficial backport of it exists in a PPA at https://launchpad.net/~chris-lea/+archive/python-django I haven't tested the package, but it appears to be a simple rebuild of what's in maverick. An official backport to lucid has been requested & will hopefully happen sometime soon.
For most kinds of software packages, I agree with you that getting them from the repository is preferable. I would argue that it's different with python development related packages, though - you mostly want the latest (stable or development) version, dependency checks are figured out automatically for you. If I were you, I'd just go with using pip.