Well, it depends on what kind of ISO encoding FM want's to use for that task, which is not always the same encoding for every task. A good example is that the hex characters work in links and forms, but not in InlineActions. This may not be the case everytime, you have to try to see how it works out.
But in general, try to avoid High-ISO characters. If you absolutely must use them in the database, you could make a relational database with all the different cities (in your example) and give them a number:
1. Berlin
2. K