Rick,
Your response sent me back into researching. This all can be very frustrating to us who know little.
Reviewing GV's requirements, I found, as you stated, that they are accepting porting from most all cell carriers and porting from a Tracfone should not be a problem. Then I uncovered a different dead end: TracFone's service status, as of May 30, 2013, is it does not support CCF, conditional call forwarding:
http://www.tracfoneforum.com/search.php?sid=58351180068e7d1bded2a33abcbf5af2CCF forwards unanswered or busy calls from the mobile phone line to GV. This feature is provided by the cell service provider, not by Google. Some prepaid carriers do not support CCF to cut costs, and TracFone does not support CCF.
I upgraded my TracFone cell along with its accessories to obtain more convenience ~ primarily hands free access in the car (bluetooth), and call screening in order to eliminate my land line and need for the answering machine for listening to incoming calls (Google Voice). My LG 840G was activated yesterday morning and last night I read that as TracFone service does not provide CCF, Google Voice call screening feature will not work.
In order to have cell phone listen call screening (versus announcement of caller ID), it seems to me that I'll have to change to AT&T's cell service. I know nothing of AT&T's cells, plans and pricing structure to compare to what I've had with TracFone. So, it is more research for me along with acceptance of the sunk cost for what I've paid for the TracFone upgrades. Recommendations will be appreciated.
Thank you, Rick.