It’s always a great idea to travel abroad to study, but my suggestion for those who are upper-intermediate or advanced would be to take an open summer course in whatever subject they would like. Instead of just studying English you could study arts, history, photography, endless options in English.
Why? Language schools – as any other business – are focused on profit (nothing wrong with that) but they will be hard pressed to place students at different levels together. In addition to that, your class will most likely have other Brazilians which will be an additional temptation to speak Portuguese. If you’re lucky your classmates will all be Chinese or Korean, so at least, you’ll have to use English to communicate with them.
Another negative point about going abroad just to “study English” – you will be paying your costs in US dollars or Euros or Pounds for content that you could have in Brazil through an intensive immersion course.
Regarding the destination, England is lovely but you will have your costs in pounds (with a still more unfavorable exchange rate than the US $) which is a disadvantage. Good options would be Canada, USA or even South Africa. Ireland would be a good option but again: too many Brazilians “studying” English in Dublin. Moreover, the Irish accent is lovely but peculiar to that country – so maybe not the best option for a first time abroad.
Again, make sure to get references from other students who’ve been to the school where you’re considering to study. I know there are schools that have poorly trained teachers with a high turnover while other schools are barefaced scams, many times cancelling the classes (for any imaginable reason) when you get to your destination and of course, you may forget any hopes of a refund.
I’d recommend cities like Pittsburgh, Portland – Oregon or Maine) or San Diego in the US or Calgary, Edmonton in Canada. Also check the weather conditions for the time of year you’re planning to go.
May the Lord bless you and your plans and dreams.