Brazil, in continuos land, is larger than US. Our country shape is like a triangle so we have a large coast also.
If you are planning a dive trip to Brazil, I would recommend you go northeast of the country. You may dive for a week in the wrecks at Recife (FANTASTIC DIVES) and then take an 1 hour flight to Fernando de Noronha and stay there for one week.Advanced OPW is recommended.
Recife is the larger city in the Northeast region and you may find good night life!!!
Fernando de Noronha is a fantastic vulcano island with amazing views and blue sea. They have what might be the only tech dive baptism in the world. Its a navy wreck at 60meters. To dive there you must be EAN certified, have 60 logged dives and go through a verification deep dive (40m).
On the other side, it is easier to fly to Rio de Janeiro in the sotheast region. Almost every airlines fly to Rio and you may find great night life here. However, diving is possible but not so good. To get good dives you must drive for about 2 hours to the north or south of the city.
To the north of Rio we have Arraial do Cabo, which is know to be one of the best places to dive in Brazil, and Cabo Frio. Both have great dives but night dive is forbidden in Arraial (idiot government rules...!!!) Cabo Frio is more prone to weather changes causing poor visibility. Less then 1 hour drive from cabo frio, we have Buzios, with great night life and diving possibility also. Arraial is less then 30 minutes away from Cabo Frio.
To the south we have Ilha Grande bay with about 365 islands. Its a great place to dive and there are many dive centres in the cities sorrounding the "bay". Angra dos Reis and Paraty are two of the cities.
At Ilha Grande itself there are a few dive centres but their quality is not good. Not much of a night life in these places.
The Northeast of the country has caribean temperature for the water: around 26/27 celsius. In the southeast, you will find temperatures usualy just above 20 celsius, being Arraial the coldest one (17 celsius).
At Recife, the sea is rough. At Fernando de Noronha, the so calleed "inner" side has calm see whiel the outer side has rough sea. At Ilha Grande bay...welll its a bay with mostly calm sea. At Cabo Frio and Arraial the sea is usually not so bad.
Of course there are other places to dive in Brazil. Bonito is in the middle of the country (fresh water). Abrolhos (Bahia) is in the northeast reagion but is between Rio and Recife. Near Sao Paulo, the biggest city in Brazil and where money runs, we have Santos where you may dive at Laje de Santos. To the South with have Santa Catarina...etc.
Hope it helps.