Cover, reduce heat and cook just until tender when pierced (about 20-30 minutes) Drain and let cool.
Peel if desired, and cut into 1/2" cubes.
In a bowl, combine potatoes, green pepper, celery, green onions, parsley, cucumber, 1/2 cup of the nuts and bacon, mix well In a small bowl, stir together mayo, vinegar, peanut butter, and curry powder, if desired.
Pour over potato mixture and stir well.
Season to taste with salt and pepper.
Cover and refrigerate for at least 4 hours or until next day.
Just before serving, stir well and garnish with remaining 1/4 cup nuts.