Compare these typical situations:
A foreigner who is a beginner in English goes to the United States. He speaks very slow, struggling English to Americans and they speak English back to him.
A foreigner vacationing in the United States speaks English to an American, and the American answers in the foreigner’s language, because he sees a chance to practice it. The foreigner tells the American to speak English, because he is in the US to learn English. The American speaks English after that.
An American who is a beginner in a foreign language goes to the country where that language is spoken. He speaks the language slowly, and struggles with it, so the local people answer him in English. He tells the people that he is in their country to learn their language, but they continue to speak English to him anyway.
The Americans, the British, the Irish, the Australians and other English speakers have one disadvantage in learning foreign languages that other people don’t have when they learn English: People frequently won’t let us practice!
What would be your advice to an English speaker on how to get people to speak their own language to him?