The sign company will not be able to cut a decal using a .jpg you will need to supply it to them in a vector format of some sort, preferably an .ai or .eps.
Otherwise, they may charge you for them to redraw it if they dont already have it available.
Just so you dont get a suprise. Also, I believe this can be found vectorized at
But a decent shop will know this and should be up front about it if they are going have to
tack on any charges for art time.
Just FYI....I'm a graphic desginer in a sign shop.[/i]