Bilingualism on it's own may not categorically prove a quick intellect but it is certainly a good marker.
Not at all. It results from a number of factors. Many people around the world have English as a second language, due to the influence of (a) the british empire and british colonisation and exploration of different parts of the world (b) US films and TV (c) literature
In the same way that French is widely spoken in morocco, in the far east etc, and in diplomatic and political circles.
And it is on a need basis - people in tourist areas (such as the coast of Portugal, (where tourism is of such importance to the economy) will tend to be able to speak english and possibly german.
The last factor is utility - in the UK, because so many people round the world do speak English, there is little incentive to develop skills in other tongues. If you take Holland as an example, the dutch often speak several languages because they are a trading nation and very few foreigners speak any dutch. So they have to learn other languages.
It has very little to do with intelligence or other abilities. Although it is very useful, of course.
This brings up the uncomfortable question, of course.
If the translations provided by the Portuguese members were in any way wrong or biased - then why? What was the point?