Spain (at least the south & east coasts) is an absolutely non-stop party. I'd vote for Mallorca (one of Spain's Balearic Islands, off the east coast near Valencia) for amazing chicks and the best beaches I've ever seen...
Of course, London's a fun city, as far as cities go. If you're seriously uncomfortable in other languages, you can have a blast there for at least a week...
Now, that said, I think you should consider making the trip to America. We've got all sorts of fun stuff if you've never been here -- I'm sure everyone will throw in a pitch for their state/region, but I'm fond of New England and most of California. Boston's my favorite town, followed by San Francisco.
Of course, there's always vending machine beer in Japan!
