I believe "interpretative clutter" in this context refers to the translations that tourism creates to reach foreign markets who are traveling from abroad. For example if I'm operating a bike rental service in Thailand, I'll likely translate my signage into the languages of the tourists that most visit my country (e.g. English, Mandarin, and French). You can imagine that such translations would exist almost everywhere in countries where the official language is not widely spoken, and they could be seen to detract from the purpose of travel--to experience something different than what one is accustomed to. The author holds the opinion that these translations are clutter.