To sum up my experience:
Northern Europe (Scandinavia, Benelux, Denmark) English is not a problem at all.
UK - I find to be quite a language barrier for some first-time native-speaking American visitors.
Germany - young people pretty much all speak English. Majority of older people (older than 50), especially in the west, speak English. In Eastern Germany it's hit and miss. I find that if I start talking in German, people may or may not switch to English.
Austria, Switzerland - everyone speaks English. I for the life of me don't understand Swiss German (along with some of my German friends).
Estonia, Latvia, Lithuania, Czech Republic, Poland, Slovakia - younger people all speak English. Older people are more likely to speak Russian. In some countries the level of perception in Russian is a bit better than in others, and receptiveness to using Russian varies quite a bit too.
In Ukraine, Belarus, Bulgaria and Russia you will generally find English spoken only in touristy places, but many young people are starting to pick it up as well.
In Italy, it depends where you are. In the north, English is not a problem at all. The further south you go the more problems you may encounter (except for touristy areas). While in Rome it may not be a problem, in Naples it will be more difficult to find English speakers. In general, the younger generation is also speaks better.
In Turkey it's hit and miss. I've used English, German and, at times, Russian.
In France, the only thing people hate more than speaking English is hearing poor, broken French. As I don't speak the latter too well, I start with it and then switch to the former. The effort is appreciated and a connection is established . It's all about the attitude.
In Spain, Castillian (which is basically what the rest of the world knows as Spanish) is spoken everywhere, including in Catalonia. English is not widely spoken even by the younger generation. When I "forgot" my Spanish (at one point it was more advantageous to do that), the guy that was not happy that I was not speaking Spanish to him and he didn't know English.
In Portugal, you'll find English spoken by more educated older people and most young people. Much easier to get around with English than in Spain. Speaking a few words of Portuguese gets you many extra points.