Since Buzios is a tropical place, mosquitoes and other insects become part of this city's life anytime of the year. You may find mosquitoes, big ants, and little spiders, if not iguanas and frogs in the gardens of even the most luxurious hotels.
Despite that, you can still enjoy Buzios at the fullest if you always carry your repellent anytime during the year, check carefully the hotel room before taking it and check it out again before sleeping. As for my personal experience, in Pousada Vila Geriba (which was a sort of bed and breakfast and not a hotel) the only problem were some ants in the bathroom the first day, so nothing serious :-)
If you need bug-killers, just ask your hotel's lodge.
I went to Búzios in November......after my Chilean Spring....so my skin wasn't really prepared for a "hot" sun. The first day I went to the beach I forgot to cover my feet with sunblock and this is the result!!!!!.........so please do not forget to cover every single square cm of your body if you'll be exposed to the sun.
Something esle were the mosquito bites.......they are "everywhere" and even when you don't feel them.....they have already had a delicious banquet with you ;o)
I bought the well known "OFF" in Búzios, that's the worst and unfortunately the only anti-mosquitos lotion they sell........but maybe you can find a good one in your country.
Be sure to exchange money before arriving to Buzios, there are only 2 Agencies and the rates are ridiculous!!
Asegurate de cambiar plata antes de llegar a Buzios, hay solo dos agencias de cambio y las tasas son ridiculas!!
On some of the boat excursions, I noticed the ocean is teeming with jellyfish. The driver of the boat will try to take you to a spot where there are fewer jellyfish, but still, you will see them next to you in the water and on the beach, so just beware.
Police in Brazil can be very corrupt sometimes, specially in Rio de Janeiro, so keep an eye on them and try to not get in trouble ;o)
You shall stay away from this animal on the beach. They can really hurt you and they are very fast in the sand. The beach I saw them was Caravelas.