Hi Larry,
I use Roland software for sign layouts but use Mach3 and GCode for cutting the vinyl so convert HPGL to GCode quite a lot. The attached program, written by Martin DeRoode of Majosoft is simple and works just fine for me. There are a couple of little quirks such as needing SP1 (or whatever pen) at the start of the code but once you get used to it, editing is no problem.
Let me know how you get on.
Tweakie.