In the beginning of the Half Blood Prince, you can see death eaters blowing up the wall to diagon alley. So, wouldn’t the muggles be able to see and walk straight into the wizard world? Also I mean muggles that have no witch or wizard within the family.
The Death Eaters flew in through the open door into the Leaky Cauldron, into the back yard, then through the (previously solid) wall that separates the Muggle world from the Wizarding world.
Since the baddies don't seem to have damaged the door to the pub, there's really no good reason to assume that the Ministry didn't prevent Muggles from seeing the Wizard world by simply closing the door.
That being said (and looking at the books), it would appear that the Cauldron already had Muggle-repelling charms cast on it. I think we can expect that these still worked just fine.
It was a tiny, grubby-looking pub. If Hagrid hadn’t pointed it out, Harry wouldn’t have noticed it was there. The people hurrying by didn’t glance at it. Their eyes slid from the big book shop on one side to the record shop on the other as if they couldn’t see the Leaky Cauldron at all. In fact, Harry had the most peculiar feeling that only he and Hagrid could see it.
Harry Potter and the Philosopher's Stone
Dumbledore handed Riddle the envelope containing his list of equipment, and, after telling Riddle exactly how to get to the Leaky Cauldron from the orphanage, he said, ‘You will be able to see it, although Muggles around you – non-magical people, that is – will not. Ask for Tom the barman – easy enough to remember, as he shares your name –’
Harry Potter and the Half-Blood Prince