If you want to go somewhere where everyone speaks perfect English, you could fly into Frankfurt, do a Rhine cruise, and also see places like Amsterdam, Antwerp, Cologne, and Heidelberg. Some really good wine country if you're into rieslings and other white wines. And of course, outstanding beers.
I agree with the May and September advice. Everyone in Europe goes on vacation in August, so all the tourist areas are swamped, especially with loud obnoxious English drunks and fat German men in tiny underpants. I've also heard that Florence and the rest of Tuscany are really lovely around Christmas time. I visited Barcelona in early January once and had a great time.
