Population: 10 million or so.
Rent: Around Ipanema and other nice neighbourhoods around $300 and up for a small studio. In cheaper but more dangerous areas, you could pay $150 for the same.
Languages: Portuguese, as in the rest of Brazil. You'll get along better with English in the upmarket areas where there are more people with an education.
Religion: Catholicism, going to the beach as often as possible and football whenever the national team is playing.You'll also see witchdoctors on the street who practice macumba or black magic.
Travel to Rio de Janeiro
Flights from Europe and the USA tend to be around $800-1000 depending on the season.
From the airport to the city expect to pay around 40 reais for a taxi (18 dollars).
Rio Weather
Being in the southern hemisphere, Rio's winter starts around May and at night it can reach a chilly 17 degrees centigrade. You might even see someone wearing a scarf but most likely not to the beach.
There are some grey days in June though and persistent rain. Then it's time go shpping and hit Rio's clubs at night.
By October, the heat is coming back in strong and the daytime temperature heads up between 35-40 once you're into summer in January.