Like the others have said, that is not valid JSON. Fixing it on the backend would be the best solution, but if you cannot - this should work for you:
NSString *dJangoString = @"[{\"user\": \"[{\"id\": \"48\"},{\"email_address\": null},{\"password\":\"f41fd61838bc65d6b2c656d488e33ab\"},{\"salt\": \"24\"},{\"date_created\": \"2013-01-27 07:59:26.722311+00:00\"},{\"date_modified\": \"2013-01-27 07:59:26.722357+00:00\"},{\"is_deleted\": \"False\"}]\"}]\"";
dJangoString = [dJangoString stringByReplacingOccurrencesOfString:@"\"[" withString:@"["];
dJangoString = [dJangoString stringByReplacingOccurrencesOfString:@"]\"" withString:@"]"];
NSData* dJangoData = [dJangoString dataUsingEncoding:NSUTF8StringEncoding];
NSError *error = nil;
id retObj = [NSJSONSerialization JSONObjectWithData:dJangoData options:0 error:&error];
NSLog(@"retObj = %@", [retObj description]);