Can mainland Chinese read Cantonese easily?
1. The subtitles are normally in Chinese (Putonghua) which is the common written language for all Chinese regardless of their ethnic groups. 2. Most HK movies are in Cantonese, but if this is a DVD, your friend should be able to switch the audio to Mandarin, which most HK DVDs have this feature. 3. In the most unlikely scenario that the subtitles are in written Cantonese, your friend should be able to understand about 70%.