Why is Winston afraid...

[Texas53]

If it isn't illegal to visit the prole section of the country, then why is Winston afraid that someone is going to catch him there?

[crazefest456]

Because the level of trust (if there was any) would go down, even if someone merely got close to something that was hated by Big Brother. Plus, at the time, EVERYONE used to go home or to the pub; it would look suspicious if someone just went off to some other region.

[Bookworm24]

Because proles and party members don't really interact much, it may look suspicious. Like Winston said in the book, walking through the prole section "was enough to draw attention" from the Thought Police which is something you definitely don't want to do. I think that's mainly why he is afraid.

[alabamagirl]

Well Texas, as you know; Winston is wearing a uniform that would stand out as he was walking through the proles. This would draw a considerable amount of attention upon him in, as the people in the proles dont wear the same clothing attire.

The problem Winston had with walking through the proles was simple; he had no reason to be there. And if he did have a reason, that would be an example of him showing emotion or interest. Something like this was too risky in Oceania, especially with the thought police and spies.