How different is Portuguese from Spanish? Are the two mutually intelligible? Because the two languages look apparently similar.?

They are close but not identical. If you are fluent in one, it is easier (not easy, but easier) to learn the other, but you would still need to study the second language.

That is, if you are born in Columbia and are fluent in Spanish, and you go to Brazil, you should be able to get along better than someone from the USA or Canada with no background in either Spanish or Portuguese.

They are different languages, but closely related. I understand it is easier for a Portuguese speaker to understand some Spanish than the other way around. The Portuguese tell a joke about how that came about. Spaniards don't think it's funny.

The US Foreign Service Institute has a section on Spanish to Portuguese.

http://fsi-languages.yojik.eu/languages/from-spani...

It's free. You might take a look.

Well, portuguese is my main language and I struggle a lot to learn spanish... go figure.

They do look alike. I can definitely read a lot of things in spanish because there s a lot of similiar words, but I can t speak it. The way spanish is spoken is just SO difficult! They definitely sound different from each other.

Portuguese native speaker can understand more or less Spanish, many words are same like: artista, dentista, novelista, otimista, turista.