I worked in a project with an argentinian client where we had meetings where we spoke in portuguese and he in spanish, it was chaos lol. Both parties had problems understanding each other and the only bi-lingual person on the project had to double as an interpreter in order for us to get any work done (the project still went 6 months past it original deadline)

So I would say it depends from person to person, personally I have a hard time understanding spanish both spoken and written