There are people out there who still manage to get looks at who actually is on and around the set on a daily basis — and AMC is not happy about those people — but it’s not the easiest job in the world now that the show’s creative team knows what to expect from onlookers.
Still, the production team did reportedly film multiple versions, as well as possible alternate takes for other scenes.
(Having a giant wall around the town was pretty good planning on Robert Kirkman’s part, though perhaps not for the people who actually live there.)
There were talks about how eleven different takes of the big death scene were filmed in order to prevent leaked footage spoiling anything, but that was mostly hyperbole.