I believe the message the song is passing is that Brazil (or at least Rio) is a really happy and beautiful place, full of music and parties!
There are just 2 things wrong with this lyrics;.
1. I think they say "wanna" not want to.
2. It's not "Party in the open evening, baby!" It's "Party in Ipanema, baby!" Ipanema is a very well known street in Rio de Janeiro. It's were Rafael (the Toucan) meets his wife, listening to the song "Garota de Ipanema" :) Então por favor mude isso! Ai tudo vai ficar perfeito! Love the website: D