Do autoupdate and autodownload only when phone system setting "sync" (aka "backround data" or "data sync" - not "mobile data") is on.

By default I have sync turned off - it prevents battery drains from some apps that try do do some background syncing even when there is no data connection and it saves bandwidth if I have to use a poor data connection for some simple explicit task (e.g. find a public transport). (I use profiles for easy tunring data and sync on and off - feature of Cyanogenmod, but there are apps in the market with a similar functionality)

I have autoupdate and autodownload set in PodcastAddict and it works pretty well. But if I have to use e.g. a poor wifi connection, PA starts to sync even though there is no chance to download all the new content and it uses bandwidth that I need for something else.

There are workarounds like "wifi filter", but using "sync" flag would be much easier and probably a more systemic approach.