You can catch Pokémon with hidden abilities in horde battles or in the friend safari.
Horde battles sometimes randomly occur in tall grass, or you can make them happen automatically in tall grass by using the honey, or getting a Pokémon with the move sweet scent and using the move outside of battle. In a horde battle, there are 5 Pokémon that appear, and there is a chance that each Pokémon could have their hidden ability.
The friend safari is in Kiloude city, which you can go to once you defeat the elite four, by taking a train from Lumiose station. To the right of the city, you will find the friend safari. Once you have talked to the person inside, you can then catch Pokémon of different types, depending on how many friend codes you have registered. And if that friend in question is playing at the same time as you, there is a chance that the Pokémon in there will have their hidden abilities.
Yes, you can catch a Pokémon in the wild that has 6 perfect IVs, but there is a very low chance that this will happen. The exact chance is about 1/887503681, which makes it almost impossible.
So, it is possible to catch Pokémon with perfect IVs and hidden abilities. But catching ones with perfect IVs is much harder than catching ones with hidden abilities, so I suggest, if you're going to get Pokémon with perfect IVs, you should do it through breeding.
Source: experience and serebii
I hoped I helped!