Under my point of view, depends on the period you plan to spend on that country. If we are talking about someone who comes just for three months , an elementary level just to buy food on the supermarket or asking for a caña de cerveza at the pub, would be enough. But if you plan to stay a long term , you will never reach a full interaction and knowing the culture if you don´t the know the local language and you will normally end up socializing just with people from the place you come from.
Not pretending to be rude, but when you say "enough people in a country" , that means you may not be really interested in taking the effort to learn , which is the easiest way most people take.
But being honest , I do understand that in the particular case of the Internet Marketer , it´s more profitable to spend time on the computer making money than learning a new language. Let me just give you this excuse