If you are paying for the fence and it is being erected on your land then you can have whichever side you like facing you. It is customary to have the good side facing your neighbours but it is not law.
If your neighbours get the 'bad' side and don't like looking at the fence posts / rails etc then they can erect their own fence, on their own land, with the good side facing inwards.
Personally, if I have forked out for a new fence then I would want to be looking at the good side.