I have a habit of putting in the garlic too early, a couple weeks before predicted first frost. That works, but it gives the garlic time to sprout before winter, and that's just wasted energy. Ideally, you want the garlic to have time to start growing
roots before freezes shut everything down, but not enough time for green shoots to start forming above ground.
I agree with other posters that it's not too late. Get them in the ground as soon as possible, then cover with several inches of leaf mulch, not plastic. Simply dumping unchopped, uncomposted fall leaves works fine.
In the spring, wait until digging in the leaf mulch shows that green shoots are forming, then remove most of the mulch so the sun can reach them.