In a large pot bring 6 cups water to a boil, stir in the barley and salt. Reduce the heat, cover and simmer the barley for 40 minutes or until tender. Drain the barley and rinse with cold water until it is thoroughly cooled, drain well. In a blender combine the white wine vinegar, garlic, jalapeno, cilantro and vegetable oil and blend until smooth. Season to taste with salt and pepper.
In a large bowl combine the cooked barley and the dressing, mixing well. Stir in the scallions, corn and tomatoes and season to taste. Chill the salad, covered, and serve.