AutoCad is just fine for Vector creation in fact it is waaaaaaay better than any
sign software. That being said I have used Autocad for many years and I will tell you how to get your vector out.
Draw it as a POLYLINE in autocad and make sure it is closed. Export it as a VERSION 12 DXF file you can do this by typing DXFOUT at the command lind and in the bottom flyout where it has the version and select version 12 or the oldest one listed. Now just import into your vector editing software.
i use autocad for my full time job "Drafting"
thats the reason why im not upgrading just yet