I agree with Techman about using Aspire. It is realitively easy to learn and use. It is priced reasonably and has great support. But this program is for 3D work. You can download trial versions of all of there software at vectric.com
What program is the person that will cut your files be using? I cut many files for other shops and I get files made from too many different programs. Exporting from say Flexi in a DXF format is usually asking for trouble as there are many types of DXF files. If you are only doing 2D signs just design in Flexi and export in EPS format. If you want to design in 3D prepare yourself for a steep learning curve.
You ask about Enroute. It is a very powerful program for doing 3D but it is very tough to learn. I have a seat that I got from a customer that uses it exclusively and like I said it is tough to learn.
The person cutting the files needs a post processer for the machine they use so they have to import your files into the program they use anyway, so just for 2D design don't spend money on software you really don't need. You can probably use what you already have.
I hope this helps.