
Alan,
Assuming you're referring to 28 as the breed mean score shown on the BVA site (sorry, feeling too lazy to check today!), then yes both parents should be lower than this.
However, if I were looking for a puppy in a breed with this serious a hip problem, I would be looking for them to be substantially lower than this - would stress that I don't know if this is realistic, as am not up enough on Newf specific hips, but I would be hoping personally for a litter with both parents scoring under 15 as an absolute minimum, and hopefully one under 10. I'm sure if this is completely unrealistic for the breed, someone will be along to tell us shortly.
My other half is actually very keen on Newfs - if we do ever buy a puppy, I will be looking at past hip scores (I have these in a KC published booklet), but you can pay the KC for a list of all scored dogs - I will then look at breeders and/or stud dogs who are consistently producing scores well below the mean score of 28. Then you can tie this in with looking at 'type' (i.e. whether you like the way they look) and of course temperament.
Big decision buying this big a dog, and there are many health risks and a reasonably short life expectancy inherent in the breed - well worth taking the time and effort to find the healthiest possible puppy. Rather wait a year and get a good 'un :D.
Hope that helps,
Marina