Just living in an English speaking country won't automatically teach you English. You could live there for 100 years and still not learn it. Some people learn English to a near fluency without ever visiting an English speaking country. The important thing is how you study it, not the environment.

Thanks a lot for your answers. The reason for many people here in italki is to learn a language practicing with native speakers, I think is the better way to learn a language. My question is focus on an specific objective when you travel for a few weeks or months to some country just for practicing and develop your language skills, keeping in mind the reason that I commented before. If somebody have had experience like this maybe could answer how much time have been there to obtain a good domain of the language.

I agree with Tony. It's not a question of time, or even of place. Someone can live a lifetime in a country and not learn to speak the language. There are plenty of people who are permanently resident in the US, Britain and Australia, for example, who speak no or almost no English. This is particularly the case with Spanish speakers in the US. You could go to the US, live in a Hispanic area and never learn a single word of English. There are also many millions of people in these countries who spend their lives not realising how bad their English is. They arrive, learn enough basic vocabulary to get by, and then carry on for 10, 20, 30 years with poor pronunciation and terrible grammar. Meanwhile, there are others who can achieve both fluency and accuracy in a relatively short time. It's all a question of attitude.

There is no rule for that. it is about how much you expose yourself into English. And you can do that without visiting an English speaking country.