DO be aware that Brazilian women can be very up front and may try to flirt with a man, even if he is out with his wife. If you don't like the attention, be cordial but not overly friendly.
DON'T discuss Argentina, religion, the Rainforest, and Brazil's class system.
DON'T ask personal questions, such as questions about age, salary, or marriage.
DO discuss soccer (football), the beach, and Brazil's growth as a country. Those are all safe and interesting conversation topics.