Django can reverse-engineer models from your database schema extremely easily. Once that is done it is 30 minutes (perhaps 4 hours for a novice) configuration and you have a working django admin site against your Rails DB.

This is how I started with Django, I migrated from hand-coded SQL to Django in one day (followed tutorial, found how to reverse engineer models and off I went).

See http://docs.djangoproject.com/en/dev/howto/legacy-databases/ for the reverse engineering bit. Tutorial starts here : http://docs.djangoproject.com/en/1.1/intro/

Give it a shot!