For creamy lime dressing, combine sour cream, cilantro, lime juice, oil and salt and set aside until ready to use.
For pork, heat oven to 425 degrees F. Place pork on rack in shallow rosting pan. Season with salt and pepper. Insert meat thermometor so that tip is in thickest part of pork. Roast uncovered until thermometer reads 16o degrees F (about 30 minutes for medium done-ness). Cool pork and cut into slices.
Arrange salad greens, bell pepper, mushrooms, peas and pork on large serving platter. Serve with creamy lime dressing.