One thing I really like about Twitter is the ability to follow what other English teachers, experts, gurus and mavens are doing. This morning, Jeremy Harmer, who definitely falls into the "guru" category, was Tweeting live from the Directors of Study conference. Reporting live from the presentation of one Guy Cook (who argues for using translation in the classroom), he sent a tweet through that...well, I shouldn't re-type it word for word, but it basically said that students don't want to pretend that they're native speakers when they're in a monolingual situation.
If I can provide another point of view...
I grew up speaking English and French, but it wasn't until I went to Prague in 1999 that I was forced to live in a situation where I didn't speak the language. To be honest, I think that it is something that all teachers of English should do. That way, a teacher can better understand the sense of humility, the frustration, the curiosity and the confusion that a person feels when trying to learn English.
I should mention that, in 1999, the Czech Republic had changed a lot, compared to its Warsaw Pact years. There were only five public universities in the whole country, and to be able to attend one, you had to have the First Certificate of English. As a result, there was a lot of demand for English classes. (There was also a lot of demand because boys who attended more than 20 hours a week of English classes were exempt from military service; and some of the boys were quite eager to learn English.) After all, if you attend university and you want to have a decent career, Czech will only get you so far. The chances of working as a Czech-speaking lawyer in London or Los Angeles...or anywhere outside of eastern Europe...are pretty small.
So most people under the age of thirty could manage to speak some English. A lot of educated people over the age of thirty could, too. But if you had to get your hair cut, obtain a visa, read a store receipt, deal with the banks, have lunch in a non-touristy area, visit the pharmacy, not get cheated by fake public transit police, buy a train ticket and not get charged double for being foreign, or try to communicate with a bus driver...good luck! It was Czech or nothing. I clearly remember one co-worker, a vegetarian from Toronto, had a really difficult time trying to have something to eat because he couldn't communicate his dietary needs to anyone. A group of us went out for lunch, and our coworker ordered a fried cheese dish called smazeny sýr. And I'll never forget the look of disgust on his face as he poked at it and muttered, "I'm SO f***ing sick of smazeny sýr that I could vomit." (He eventually got a Czech girlfriend who translated food sayings for him.)
What I'm trying to say is this: No language learner ever wants to forget how to use his or her first language, but there are times when you have to behave like a native speaker, even if you don't particularly want to, and even if you know that THEY know you're not native. Does it suck? Of course it does. I'm not going to say that it's easy, that it's fun, or that it saves you from embarrassment 100% of the time.
There's another problem: translation only works if everyone in the classroom speaks the same mother tongue. Even in Spain, that's not automatically true any more, unless you're in a one-on-one situation. What happens if you have students from Morocco or Brazil or Romania in your class? Do you automatically assume that their Spanish is as good as the Spanish of the rest of the students? What do you do if it isn't?
Three months after I arrived in Prague, I started Czech classes. Our teacher, Petra, spoke wonderful English, but she did NOT speak it in class. In the first class, we were given a page with common expressions. If we couldn't say what we wanted to say, we had to wait until the end of class, or try to put together sentences to tell her what we wanted. (And if you've ever tried to learn a Slavic language, you know that it's not as easy as putting words in a set order.) Was it comfortable? No. Was it easy? No. Was it effective? You bet: the minute we stepped out of the school and had to do anything in our lives, we were prepared for it. I only took one semester of Czech, but I'm proud to say that I still remember how to count to ten, how to order 100 grams of ham and how to ask for aspirin in the pharmacy (lekárna!). I admit that in the nine months I was there, I was never brave enough to get a haircut in Czech, but I learned how to stare down a corrupt police officer and paid 50% less for my train tickets than other foreigners.
Translation may be helpful, but it isn't always effective.