Google served you ads in English, because while you told translation to convert the page, for example, into French, the default language of the computer you were using was English. The ads are based on the 'user' which is detected by the actual machine settings as are screen resolution, browser platform...
If you were at an internet cafe in France, as an American speaking English, it would be up to the cafe to change the default language of the machine to suit your needs or to provide a proportionate number of English machines (at least one) that utilized the most common second language.
Otherwise, you are surfing the English speaking web, if that is your preferred language, with crappy translation. Translation software, while having come a long way in recent years, is far from a desirable solution.
Since I surf the web in many languages as part of my research, I can tell you that it would be preferred to be on a machine set to English rather than to translate everything into English on a French machine. Because I surf the web in other languages for research, those ads will never be clicked, no matter what language they are in.
If they were on your site, your loss is that I came to your site to begin with, no matter what language I come in or translate to, because I am not going to click any ad on your site. It would be a waste of my research time. I will come back to this point at the end of my comment. I suggest, that only people doing research, would deliberately surf the web with a translation program in this day and age. People doing research do not click ads, nor should they.
If you are paying to work on a machine that is not defaulted to the language you speak, the owner of that machine has failed you, not Google.
However, in this day of low cost, fast laptops and wireless internet in many homes and hospitality industry properties, as well as many coffee houses and restaurants, I don't know why anyone capable and savvy enough for internnational travel would use an internet cafe to begin with.
Internationally, I think internet cafes are primarily filling the needs of locals who are either too poor to buy their own machine and service, or too rural to get internet and they speak the primary local lanugage. While internet cafes originally served the needs of the business traveler, because hospitality had not begun providing these services, hospitality has now largely caught up, even within the worst and most budget motels. A $60 wireless router is within the budget of the smallest mom and pop B&B or motel.
When people come to my home or office, they open their laptop and go to work on wirelss. So, if a friend came in from Holland, they would likely surf the web in my home, in dutch, the default language of their machine. The ads they would see, would be in Dutch. The odds of a friend coming in from Europe and not bringing their own laptop with them, is nil.
This is the same odds of me traveling to Holland and not taking my laptop with me to use while I stayed at a hotel that offered internet.
This isn't 1999, it's 2009. You are applying a situation that is not realistic. One Adsense publisher surfing the web to test Google, does not a target test group make.
Where money is being lost is having these visitors come on some type of a pda device. They comprise 3% of my traffic and do not see the ads. I know, because I surf my own sites with my blackberry as well as with less smart cell phones. Those visitor numbers are increasing, and really pose the biggest problem to Adsense publishers in the comimg decade, as their numbers are sure to grow significantly. This isn't google's fault, it is mine, for not developing (yet) a mobi site for that particular internet property, while I have done so for some of the smaller properties I own.
[edited by: MsHuggys at 3:11 pm (utc) on June 27, 2009]