B&O Jim,
there is no easy way to answer this question. If you are using TMCC 1 to run TMCC 1 trains, the answer is yes, turn the Ody off, providing the loco has an off switch installed. If you are using Legacy, and running TMCC 1 locos, put the "control type" in TMCC mode, this will send absolute speed step commands to the locos which SHOULD make them play nice together. If you are running Legacy locos, leave Ody on, everything will work fine.
Now, all of that applies to Lionel TMCC 1 locos. Add in K-Line cruise, ERR Cruise Commander and EOB and things get even more complicated to answer clearly.
The easiest way to find the answer is to put 2 or more locos on the track together, program the lash up and run them. If you hear the banging sound made when the couplers smack together, then turn ody off, as you will be replacing traction tires at an alarming rate!
hope this helps, a little!
thanks,
Mike