You're right.Your dress code speaks a lot about you, so if one is going for an interview no matter where the organisation is located, you have to appear in an office wear and not a casual wear. Have it in mind that you will be asked any sort of questions which in some cases might have nothing to do with the company. But always have an idea about a company and their products because this is always one of the questions asked.
When going for an interview, I think putting on something formal is really cool. Whatever you get to say should be based on the questions asked you, you should be polite in answering them.