Purée first 6 ingredients in blender until almost smooth. Season generously with salt. Pour dressing into medium bowl. Mix in hominy, 1/2 cup cilantro, jicama and onion. Let stand for 30 minutes.
Steam potatoes until tender, about 30 minutes. Cool 15 minutes; peel. Cut lengthwise in half, then crosswise into 1/2-inch-thick slices. Place in large bowl. Add hominy mixture and toss to blend. Season to taste with salt and pepper. Sprinkle with 1/4 cup cilantro. (Can be prepared up to 2 hours ahead. Cover and let stand at room temperature.).