Hey James,
I agree with everything in your article. However, I think there is a phenomenon where people, not travelling and in their home country, insist on speaking to every foreigner they meet in the foreigner's language. I think this can be extremely bothersome to the foreigner, the foreigner's reaction will be bad, and the learner will be discouraged.
To explain:
I have a bad habit of looking at my colleagues' lesson plans at the school where I work. One teacher had planned an entire lesson based on the scenario that the student stepped on the bus and saw an empty seat next to a foreigner. What a great opportunity to speak English!... at least according to this teacher.
In reality, the foreigner might not speak English, might be in a bad mood, might simply want quiet before or after work, or actually be the nefarious type of person you don't want to encourage young language learners, or young people in general, to talk to. The student, I imagine, would come out of the experience never wanting to speak English, even when travelling.
Really enjoyed your article!