Cook noodles according to package directions. Drain and rinse with cold water to prevent noodles from sticking together; reserve.
Combine the curry paste, coconut milk, half the cilantro, lime zest and juice, salt, and pepper in a small bowl; mix well. (This mixture may be made up to 2 days ahead; refrigerate in an airtight container.) Transfer the steak to a roasting pan; rub with 2-3 tablespoons of the curry mixture.
Broil (or grill) the steak until medium-rare (about 4 minutes per side); transfer to a plate.
Arrange scallions, carrots, cucumbers, and reserved noodles on a large platter. Brush steak with more curry sauce. Thinly slice steak, and transfer to the platter. Drizzle remaining sauce over salad; sprinkle with remaining cilantro, peanuts, and mint.