Cantonese is the primary language of Macau, and Mandarin is also understood, but not preferred. Unlike Hong Kong, English is seldom spoken or understood in Macau. The Wynn is a noteworthy exception, where some degree of English seemed to be required of front-line staff. At the Australian owned Crown casino I had great difficultly asking about the game rules, and had to resort to drawing pictures of cards on the table. I was there before the Venetian opened, so I can't comment on how you will fare there with English there. To make matters worse, if signage is in two languages, the second one will often be Portuguese. What little Spanish I know was helpful, which has a lot of crossover with Portuguese.