To put a mesh grill on Chrysler 300 do you have to take off the bumper?

Generally, yes, you will likely need to remove the front bumper to install a mesh grill on a Chrysler 300. The grill is usually mounted behind the bumper, and accessing it and securely attaching a new mesh grill requires removing the bumper for sufficient working space. While some minor adjustments *might* be possible without removal, it's highly uncommon and significantly more difficult. Most installation guides will explicitly state bumper removal as a necessary step.