Place potatoes in a medium size saucepan and add enough cold water to cover by 1 inch.Lightly salt and bring to a boil.Reduce to a moderate simmer and cook for 15 to 20 minutes or until fork tender. drain.
Cut potatoes in halve or quarters, depending on the size, so each piece is about 3/4 and inch.Place in a large bowl with green pepper,onion, manzinilla olives and cilantro.
In a bowl, whisk oil,vinager,salt and pepper.Gently toss with potato mixture and let stand, covered at room temperature until cool.
Serve at room temperature or chilled.(I prefer chilled).