You can, but I'd use newspaper or cardboard instead of plastic.

agree with lynnmarie

The rcycle place or a place that ships in solar pannels is a great source for large sheets of FREE cardboard.

If the grass is bermuda, nut grass, or johnson grass, then you may need to kill it first before you put down the cardboard. I'm developing a 'dead plant' policy where those three are concerned before planting anything else where they might have been growing. ymmv.

I totally agree with you, merrybookwyrm. Bermuda will come back even from the dead.