But as a geek, I am flattered that you asked and can't keep my virtual mouth shut. The short news on the subject is that MT doesn't work but that MT is getting better at not working. MT, my droogs inform me, will always be doubleplusungood cuz folks mess their language up a bit right regularly. You begin to see the problems, I hope. Speaking the language into a MT device doesn't crack these problems.
Spoken language adds other interesting problems to the mix.
Still, some translation is better in many cases than no translation at all. Companies like Franklin and Lingo make cute little helpers that will get you through some sticky places when traveling. Purely for scientific purposes, I'll reproduce a sample babelfish session here. A cheap shot to be sure, but one that points up the problems inherent in MT while providing a little amusement. What you might try instead is a mix of human and machine translators.