The Palace crossing isn't wadeable until it is below 2 ft on the rock guage. At 2 feet, the crossing is deep and fast, but feasible if you know where to go and have a wading staff; 1.75ft or lower is better.
Check out the free downloadable guidebook on the NC3 site if you have more questions about Poudre wading levels or other approach logisitics. Full color, detailed beta to the Palace (and other areas that are climbable at high water) is available for free.