I think that the main significance of the setting where they meet for the first time is that it corresponds perfectly to the setting that Winston has a recurrent dream about. He tends to dream about this place that he thinks of as the "Golden Country." (We see this in Part 1, Chapter 3.)
In this dream, he sees a young woman take off her clothes and beckon to him. He is taken by how free and graceful she looks and sort of envies her this freedom. When Winston meets Julia there, he is essentially having this dream come true. With Julia in the Golden Country, he will try to become free.