Mike Manaro,
What other Gcode will that machine recognize? Does it permit commands in the machine coordinate system (G53) as well as the work shifts G54-G59?
I'm not sure why, if you move to the work datum, that you would want anything other than G92 X0 Y0 unless the control is keeping track of where the work home is relative to the machine home.
If the machine is parked at machine home and you want the work datum elsewhere, then, IMO you use coordinates with G92 X and Y to designate that the work home is not at the present location but is elsewhere. In this case, the signs should not need inversion.
If possible, I prefer to use a G53 line before a G92 line because this forces the machine to move to a known position in the machine coordinate system before the coordinate system is shifted by the G92. This can help prevent crashes after a program is aborted but the operator must always start at the beginning of the program to ensure that the G53 is read. Either that, or start from machine home.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)