Thank you for your response.  Unless I'm on a plane, I will have the cellular data connection on.  And I haven't noticed any difference.  I have fiddled with a few settings.  Currently, "Sync over WiFi only" is OFF.  I haven't found a way to force the download to happen.  At this very moment, I have two texts that show downloading.  I am certain that they are group texts/responses.

It's a bit frustrating.