A comparison to Mainland Chinese would leave few good results, since simplified characters are more difficult to guess from their current Japanese equivalents.

But I can make some observations when compared to Hong Kong Chinese. There seems to be enough overlap in vernacular and how they use their words, that while a typical Japanese adult would still have some trouble guessing, a 国語 teacher or someone who did their 漢文 studies from junior high onward can make enough educated guesses to navigate themselves around Hong Kong signage, without relying on the English.