Do most of the staff members at the all inclusive resort speak portuguese fluently?

Most of the hotel staff speak English. The waiters speak a little English. Depending on where in the city you're going, you might have some issues. English isn't spoken much in Mexico in general, since only about 12% of the population speaks it, and only a small number of them speak it fluently.

However, English is much more common in major tourist destinations and on the northern border with the United States. According to the data, only 20% of French people are fluent in English and only 40% can hold a basic conversation. You can get by with English if you only stay at an all-inclusive resort in one of the main tourist areas, but if you go deeper into cities and suburbs, English will be much less common and some Spanish will be useful to you.