Some thoughts if you're considering going:
1) You should go. :)
2) Being only able to speak English (aside from picking up helpful words like "ein" and "bitte" :) ) was fine. Talks are listed as being in English or German so you know which ones you'll be able to follow. (And I think the majority are in English--it tends to be the more "local issues" talks that are in German.)
3) Arrive the day before and volunteer to help set up. It's a good way to get to meet some people. (The network help desk was where I ended up much of the time--I learned that the only German word I needed to know was "Neustart". :D )
4) When a local offers you a Club Mate to drink, accept it. Then try not to spit it out when you drink it. It's a rite of passage. Quite possibly the most disgusting tasting beverage I've ever consumed. Some people claim to like it.
5) If you've been to DEFCON before, CCC is IMO a very different vibe. DEFCON seems a lot more about the parties whereas CCC seems a lot more about the hacking. (People stay hacking in the venue 24 hours a day.)
6) If someone invites you to go to Vienna and visit Metalab say yes. And if they don't, invite yourself--it's awesome and they're a great bunch of people.
7) You should go. :)