The 21-year-old was released by the Ashton Gate side in April 2001 and had been playing at non-league Atherstone United before Allner handed Spencer a trial with the Whaddon Road outfit this pre-season.
He scored two goals in a 45 minute display during a pre-season friendly against Conference side Forest Green Rovers and Allner may be ready to keep the goal-scoring youngster for The Robins' new campaign in Division Two.
Spencer made few appearances for Bristol City since turning professional in August 1999 and manager Danny Wilson decided that Spencer had no future with the Division Two club.
Should Spencer sign on with Cheltenham for the new season, it will be his second spell in Division Two football, following his intervening period in the Dr. Martens Western Division with Atherstone.
