Definetly stay either in Saint Jean Cap Ferret
it's a lovely place.. or better your idea of St Paul de Vence!
We love the hotel there called
La Colombe d'Or.. it's wonderful.. and if you don't stay there- a must to have lunch on there vine covered terrace. Food is delicious and then there is just being there.. Their main dining rooms walls are covered with priceless paintings.. just unreal.. when the artists were starving they traded their works for room and board..
I was looking for their website and found this:

"In days gone by, visitors to this small stone-built Provençal-style hotel stood a good chance of bumping into artists such as Matisse, Picasso, Miro and Léger. Now visitors are more likely to bump into actors and celebrities including the Beckhams, Elton John and Roger Moore, who go to eat in the hotel's renowned restaurant, which serves up good Provençal cuisine. But the artists have left their mark - many were cash-strapped when they stayed, and so paid by leaving some artwork, which is displayed in the restaurant. The hotel has added to those donations to build up a surprising collection of art. There are also sculptures around the outside pool, including one by Calder. Each of the 26 rooms, which include 11 suite apartments, are decorated differently. The hotel is just at the entrance to the village of St Paul de Vence, about 15 minutes from Nice. "

Here is their website
http://www.la-colombe-dor.com/dove/hotel.htm