Judy, when you install SBE, choose any machine driver and default COM, it doesn't matter because you are not going to be using the program for cutting according to your description of how you intend to do this.
However, because you want to mirror the image in SignBlazer, you'll have to do it a different way than just clicking the checkbox in the cutting screen (because you aren't cutting with it).
The alternate method is to create your design in SBE, and then "select all" which will put a box around it with handles outside and inside (the outside handles are for adjusting size). The inside handles are in the shape of an inverted T and you'll see three handles/points. The top one is for rotating. The right hand one is for skewing. The left hand one is the important one for you, because it MIRRORS (flips) the entire selection. VOILA.
Now, with your backwards design, export it as .eps (File menu: Export) and you should be able to deal with it in your Cricut cutting program.