It would have to be at least 10 meters to facehug him, and are we all forgetting about this:
Take a look at a few of the pics where he's shooing his beam. He's got a pretty simple solution if something latches onto is face... Plus,he regenerates, so even the acid blood won't have a lasting effect. Even if it did manage to get a chestburster in there, it would either 1. Die of radiation poisoning, 2. be incappable of ripping through his skin, or 3. rip through and get blasted. Again, Godzilla's regeneration would repair the damage.