Welcome to my part of Germany!
If you need help, information or directions in English it's best to approach younger people... they all speak English to various extents: some only have "highschool-English" and others speak it fluently. Strange as it may sound, it can be quite difficult to find a local when you need directions... there are usually so many visitors (especially in the old town) that I've witnessed many tourists accidentally asking fellow tourists for help: "Do you know where this street is? Sorry, I don't live here either!"
Nevertheless, any person anywhere in the world appreciates if you make an effort to approach them in their mothertonge (well, everyone except the Parisians...)
Here are some common expressions you might need
(I will write them phonetically)
"Shprechen see english?" = Do you speak English?.
"Ich bin tourist. Konnen see mir healfen?" = I'm a tourist. Can you help/assist me?
"Antsholdigong, haben see dee zeit? " (like "eye") = Excuse me, do you have the time?
"Antsholdigong, vo ist...?" = Where is ...?
"Fielen Dank" = Thank you (very much).
"Reichnong bitta" = The bill/check, please.
Heidelberg is part of "Baden Wuerttemberg" in the South-West of Germany.
As in any country, different regions speak different dialects, different slang & very different accents. A good info portal on my home-state is http://www.baden-wuerttemberg.de/en/index.html
--> Unless you speak German, you probably shouldn't even ATTEMPT to understand some of the funny dialect expressions down here in the German south. For example: there is a hotel & restaurant close to the old town bridge called "Snookeloch": Schnooke is dialect for "Muecke" which means "Mosquito / Gnat". Loch is "hole"; so it's the "Gnat's Hole Hotel"... don't ask... just click on the picture to see it... hahaha! :-)
--> The "motto" of Baden Wuerttemberg is: "Mir koenne alles, bloss koi Hochdeutsch." (We can do anything, but we can't speak "high" German)
On the way to the castle, we were standing in the middle of the street looking at a map and this little old lady came from nowhere and asked us if we needed any help. Her bit of advice to us was 'Just stop and ask, everyone speaks english.' This is very true. However, they tend to appreciate it if you make an attempt to speak to them in their own language...so try to brush up on a little German.
There were always quite a few tourists in Heidelberg as I was growing up and there seems to be more every time I go. Some of the locals can be rude if you look like/act like a tourist. You're best bet is to try and speak a little of the language. It would not be hard to find someone who spoke english as most germans, especially the young ones speak it. But they are so impressed when you make an effort to speak their language.
Now that you're in the South, South west, Central, or West part of Germany, I noticed that people are much more traditional in their speaking. For instance, you'll often find complete strangers saying the formal greeting of 'Guten Morgen' to you out of no where. Also, they seem to say 'Tschus' alot, I doubt I spelled it right, but it's an informal goodbye.
While traveling to foreign countries like GERMANY, make sure you try the local foods - and pleeeease do not compare everything to home (prices, quality etc.) because you are not home. While some foods and beverages may seem odd, try them and appreciate them. Anyway, German food is not odd tasting at all. In fact, it's tremendously delicious! I, for one, am a real sucker for their world-famous Frankfurters. Yummy! Sample local fares at local cafes and be friendly and courteous - always. Hey, we don't want them Germans to come complaining that VT members are an uncouth bunch, do we? :-D
When visiting a foreign city like HEIDELBERG or any parts of Germany for that matter, do carry a matchbook or postcard with the name and address of your hotel, which you can show to cab drivers or when asking directions. Not all Germans speak English as well as you/us...and we certainly don't want the cab driver(s) to drop us off in some infamous Red Light District, n'est ce pas? ;-) I thought so too.
Speak Their Lingo!
There are not many countries where the people aren't absolutely delighted for you to try out their language. And Germany is no exception. If you use just the word for 'thank you' i.e. 'Danke', they'll be impressed. Trust me. If you know more about their language, even if you are not fluent, you'll find yourself learning more about the real people, not the ones shown to us in movies! Germans are really a delightful bunch of people who are intelligent, diligent and take pride in their work.... They are exactly as curious about us as we are about them! :-D
Here are some German slangs which you might find helpful! Thanks to my dear friend, Martin for these translations... :-)
How are you?
Wie geht es?
Pronounced as: Vee Gay Tess?
See you later?
Pronounced as: Vee Tess Sane