Yes, it's the only way to get to all the bolts and mounting bracket with out the chance of damaging anything including your new grills.
It's actually quite easy to do. Just take your time and while your at it, you ca take off the upper support or filler panels and repaint it all. That's what I ended up doing after noticing a few scratches and nicks... just took everything from the radiator core support off, sanded & repainted it all, and it looks like new.
Just make sure you apply some pressure when reassembling and aligning the bumper to get an even gap between the fenders and the bumper on both sides. Then tightem the bolts good and tight!