I don’t think that locals desperately want to speak English as often as possible, but rather to be polite. If what-the-person-in-front-of-me-speaks is barely recognizable as Swedish (accent/broken grammar), and I can assume that both of us speak English, I think I’m doing both of us a favour if I switch.
I haven’t had any problems learning a second language. I have met people who want to learn English and want help with that but don’t really want to help you as much to learn their language, on the other hand there are a lot of helpful people around so it hasn’t been a problem. I talk mainly in (broken) Russian to a friend online and she responds in English half the time but I don’t mind, what matters is that she understand what I’m saying.
I’ve very much had the same no matter where I go, apart from Spain, where very few people actually spoke or even wanted to speak English, even though my Spanish was pretty bad. And I lived in the Costa Del Sol and not some small village in the middle of nowhere. I also found the same in Milan, not that many people spoke English very well (Only enough to do their jobs).
If someone starts a conversation with me in English, I’ll continue in English. If I start a conversation with someone in let’s say German, and they answer me back in English, I’ll just continue in German unless I struggle and it starts to kill the conversation, etc.
From experience, I think it boils down to confidence, if you speak clearly, loudly and don’t look like you are really struggling and sweating, then the other person will continue to speak to you. If you look shy, scared, then the other person will probably just answer you back in English.
In most cases, you can’t blame the people in touristy places, since so many people from different countries just communicate with each other in English, almost as if it is automatic.
I’ve found that older Italians (age group 50+), in general, don’t speak much English at all which seems to be the case in a lot of the rest of Europe.
In Sicily and Sardinia this seems to be even more the case, though in the north knowledge of English is quite widespread, amongst the young at least.
Though I’m still far away from being fluent in Spanish, I hardly made this experience with Spaniards during my stay in Spain this year (in Sept. - Oct.). Only in Barcelona I got 2 times a response in English. But my main problem was, that we lived in an urbanization with only very few Spanish people (the most were from England, Germany or the Netherlands). The next small town were about 3 or 4 km away. So - unfortunately - I only had very few practice. In France - as supposed - nobody replied in English.
But maybe the reason might be, that English is only another foreign language for me.