Just remember this will set the units for the current scene.

When you save that scene you changed the unit for they will be retained but any new scene will switch back to the default units of centimeter.

I used to think that Maya switching back to centimeters for all new files was a bug but apparently it is by design. You can go into one of the Maya startup files and set the default to a different unit. I can't remember the path, it's been a long time, and I was advised against it.