I must be honest here, if you cannot speak the language, you are subjecting yourself to potential misunderstanding (and abuse), as clearly illustrated by the case that this thread started with - in the end the fine was squashed even though in the beginning it seemed impossible.
There are many nuances in life which simply get missed if you do not understand. If you can only pick out one word of every sentence how can you expect to do things properly.
Obviously there are those people that take advantage of this. As I am sure there are people in the UK that take advantage of foreigners that cannot speak the language...
That said, I am simply amazed at how the Spanish themselves, allow themselves to be abused by the government, large corporations (utilities) and public administration... ...erm not much different to UK then?
We need a bit of the French revolutionary spirit in both countries!