It always comes as a surprise to me that Russian language skills are in such demand for projects in Central Asia and the Caucasus. Radio Free Europe just ran an article asking if the Russian Language is Dying out In the Former Soviet Republics? In many republics, it most definitely is. If you think you're going to conduct your opinion research in Azerbaijan, for example, exclusively in Russian you're making a huge mistake.
According to the article, only five former Republics still use Russian as an official language -- Belarus, Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan. In Ukraine, it's not an official language but a large proportion of the country (the East) speaks it exclusively (with an almost as large proportion, mostly in the West, who refuse to speak it).
In a place like Azerbaijan, it's more complicated than just a decline in the number of Russian-speaking schools since the Soviet Union collapsed. There are political and social factors to consider as well.
During Soviet times, all "educated" people spoke Russian. In fact, you meet plenty of people who grew up in Baku who have secondary and university educations and who never really learned to speak Azeri. Since many government officials got their start during the Soviet period, it's not uncommon for even high ranking officials to not speak the national language very well.
On the other hand, those who are very well-educated, and nationalist often refuse to speak Russian since they view it as a colonial imposition. When I worked in Baku, I rarely attended meetings in which Russian was the medium. Hearing their President speak Azeri grates on many and they mock leaders who are less than fluent.
These days, young people might only be learning Russian as a foreign language, unless they attend a Russian school.
It's different out in the regions, where the Soviet-education system didn't penetrate very well. Very few people speak Russian at all and even fewer are learning it now. The very well-educated and the least well-educated actually share a common tongue.
Even though Azerbaijan's population is largely urbanized, conducting your research in one language or the other will exclude some people and exclude others so you need to use both. Similarly, in Ukraine survey instruments need to written in both Russian and Ukrainian, in order not to exclude those in the East who don't speak Ukrainian at all or those in the west who refuse to speak Russian. Focus groups in either country need to be segregated by language, as some people are much more comfortable speaking one than the other.
This language puzzle makes getting in a taxi in Baku potentially tricky as well: Is the driver in from the regions and therefore, non-conversant in Russian? Is he an ordinary middle class Bakuvian who has spoken Russian his whole life? Or is he a moonlighting history professor who hates Russian and will speak only Azeri? You can never tell (at least until he starts driving).