|It's easy to start a conversation with people on Livemocha|
From what I have noticed, messaging people in another language that you both speak nets you better results than just messaging them in English. However, searching for people in the particular language where that language is spoken will yield you much fewer results. Perhaps it is because these people have the premonition that they are there to meet other people through the site. But hey, you could do a lot worse with your time online then not socializing.
If you are self conscious about creating a dating site profile because people you know might see you (in the process of looking for partners I found one of my TAs as well as a fellow students who was looking for casual sex) you can always say at the top of your profile page that you're only interested in talking with, or possibly meeting people who speak the language you are trying to learn. Your profile can also say that you are in a relationship or seeing someone. Of course if you are seeing someone, it wouldn't hurt to let your significant other know what your intentions on the site are.