Please, remember that the seasons in Brazil are opposite to those of the Northern hemisphere. So, warm weather is expected for the EIBA 2015 conference.
Brazilians (and Cariocas, in particular) tend not to be too formal as regards dressing for business and social occasions.
At the conference
Casual business attire is recommended.
Since the weather is expected to be warm (probably between 22°C and 30°C; 72°F and 86°F), light clothing is suggested. Although jeans are acceptable, slacks and trousers convey a more welcome sense of informality. Shorts are definitely not suitable for conference delegates.
Women can choose to wear dresses, skirts or slacks. Men can wear either short- or long-sleeved shirts (in this case, rolled up sleeves are quite acceptable) or even polo T-shirts. Blazers can be worn by those presenting, but this is not a rule. A suit and tie are expected only from those in more formal or official roles (e.g., keynote speakers), but if you feel better in a suit and tie as a conference delegate, that is fine too.
Casual footwear – sneakers, tennis shoes or informal shoes – are acceptable, but slippers and flip-flops are not. (Note that Havaianas are suitable only for informal occasions…)
At the gala dinner
The same dress code as above applies. However, since this is an evening event, some men may want to take a blazer or a sports coat along. Women may wish to wear a long, formal, dress – but this is not a rule. However, please remember to bring comfortable shoes and clothes in which to party all night! Let’s celebrate one more successful and enjoyable EIBA conference!
For leisure activities
Dress as you wish. Cariocas are quite tolerant, diverse, and they enforce no rules. If you would rather be a bit less casual, that is your choice, but if you prefer to really enjoy the Havaianas and sleeveless shirt style, or the mini-skirt, that is fine too. When in doubt, do as the Cariocas do.