Prepare outdoor grill for covered direct grilling over medium-low heat.
Meanwhile, in microware-safe 2-cup liquid measuring cup or medium bowl, combine vinegar, brown sugar and soy sauce.
Heat soy mixture in microwave oven on High 3 to 4 minutes or until reduced by half.
Pat tenderloins dry with paper towels.
With 5 pieces of string (each about 6 inches long), tie together pork tenderloins; sprinkle with salt.
Place tenderloins on hot grill rack. Cover grill and cook tenderloins 20 minutes, turning to brown all sides.
Place peach halves on grill rack.
Cook peaches and tenderloins, uncovered, 8 to 10 minutes longer, brushing all sides frequently with soy mixture. Cook until peaches brown and soften slightly and pork reaches an internal temperature of 145F (center should still be slightly pink).
Place peaches on cutting board; cut into bite-sized pieces, then transfer to small serving bowl. Remove strings from tenderloins.
Cut tenderloins into 1/4-inch slices; top with peaches to serve.