§ the giant sinkhole

Instead of entering the actual caverns, you could skip all the poisonous Pokemon and go straight to an area called the Giant Sinkhole. To left of the caverns entrance is a path that leads to a large hole in the ground, which is populated by Bug-types. This area doesn't have radiation, so you can stay here for as long as you'd like.

If you're tired of being in the sinkhole, you can very easily enter the caverns. On almost every wall in the sinkhole is a hole that leads back into the caverns. Just be careful when you go into them, as you'll be exposed to the poisonous radiation!