Rio de Janeiro actually has many opportunities for language classes. It is highly recommended that you learn Portuguese as it will not only improve your day to day interactions, but allow to dip past the surface from tourist to resident. Luckily, there are many different ways to learn Portuguese in Brazil.
If you prefer to study at home, online classes may be perfect for you. There is also the ability to study online before you even enter Brazil. Two such schools are www.learn-Portuguese-now.com and www.studylanguages.org.
Berlitz International Inc - Berlitz has two schools in Rio de Janeiro and is well-known throughout the globe.
Instituto Brazil-Estados Unidos (IBEU)- This school primarily caters to Brazilians learning English, but classes to learn Portuguese can also be arranged. This cultural and language institute has fourteen branches in the Rio de Janeiro area.
Fast Forward Language Institute - Provides quality Portuguese language programs in a professional and friendly environment.
Step1 Idiomas - This is a program that combines language classes exploring the many tourist attractions of Brazil. Contact: firstname.lastname@example.org