In the morning, drive south on Route 89 and cut across the Tushar Mountains, the third-highest range in Utah, on State Route 153. You'll then take I-15 south for about an hour, until you arrive at Cedar Breaks National Monument. This rocky, three-mile-wide and 2,000-foot-deep hoodoo-filled amphitheater looks almost like a smaller Bryce Canyon, and doesn't open until the snow melts in mid-may. In the summer, stay at Point Supreme Campground for $14 per night, no reservations necessary. If you want something less primitive, you can spend the night at nearby Brian Head Resort ($225 per night).
Now it's back to Vegas, only three hours down I-15.