Portuguese language is a must to operate in Brazil. Brazil is awesome. If you want to live in Brazil, that is reason enough. Here are some other reasons to learn Portuguese:

1. Portuguese is the most common language in South America. Brazil is only one country, while most of the other countries speak Spanish, but South America is really split in two equal parts by population and land mass. The Portuguese half is one large diverse country, while the Spanish half is split into many different countries.
2. Portuguese is rare for Americans. After almost 4 years of going to Brazil now, I have met only 3 other non-Brazilian Americans who speak Portuguese. I have met maybe 5-10 who went to Portuguese language training by the US government for specific jobs, but they are on government career paths and do not seem likely to remain in Brazil once their assignment is complete. If there appears to be no demand, I would argue that zero supply prevents companies from seeking it because of the extreme rarity.
3. You get a two-fer. Spanish comes along with it. This is true. Portuguese and Spanish are indeed similar. I recently attended a history lecture in Rio where the French lecturer did not speak Portuguese and he assumed everybody would understand Spanish. I understood his Spanish better than the Portuguese from Lisbon! Expose yourself to some Spanish along the way and you will see what I mean. After I visited Colombia for 3 weeks, I had to buy a Portuguese-Spanish dictionary to separate the languages in my head.
4. Learn it “all the way.” You have to live at least 6 months in the country immersed in the language. Commit. Until you do this, the language is not really useful.
5. Portuguese is easier than Spanish. I really believe this. People say Portuguese pronunciation is more difficult. I disagree. Portuguese has maybe two sounds we don’t have in English, the nasal -ã and -ão. They do not roll their ‘R’s. The Portuguese grammar is closer to English also in my opinion. Not so many ‘lo’ and ‘la’ and ‘le’ for no reason like in Spanish, less use of reflexive verbs, and overall fewer syllables.
6. São Paulo. São Paulo is the business capital of Brazil, and by far the largest city this side of the Atlantic. São Paulo speaks Portuguese.
7. Don’t forget Portugal! I have heard it’s nice! I have never been, but Brazil and Portugal are not the only Portuguese speaking countries. See the Community of Portuguese Language Countries.
8. Learn a language, any language! Once you really learn a language as an adult, your next one will come so much easier. It becomes less of a magical impossibility and more of a travel task of a few weeks or months to get practically conversational.

I scored “Advanced Low” on the ACTFL Speaking. I think “Intermediate High” in a language would be good enough to get started working in a foreign country. At my level, I can easily communicate, network, and socialize, but I should still improve to continue here. I scored Intermediate High on the ACTFL Writing.