Whemy, if by vocals you meant people singing a lyric, then no, by no means should you use vocals. Lyrics and games don\'t mix, as people have radical variations in taste.
Senseless vocals, such as a chant add to the atmosphere of a game, ala Final Fantasy VIII, the music that played whenever Edea appeared. Not a good game, but FF\'s have always had brilliant soundtracks.
Any vocals should be completely incomprehensible.
As for different music for different locales... Temples should be accompanied by soft \'holy\' music. Willaert\'s link was broken by the time I saw this thread, so unfortunately I haven\'t heard his sample.
I believe a tavern should have a lively, jumpy beat to it. They are places of merriment afterall, and not meant to be melancholic. If the aforementioned tavern were to be a seedy, dank establishment, then naturally it would be accompanied by equally dank music.
Wonderful examples for audio are the Baldur\'s Gate games. Never let it be said that Black Isle and TSR don\'t create an immersive world, such as that working on PS no doubt wish to create.
The music is a reflection of the atmosphere. As I said before, unless it is in a temple or similar place of worship, the music should be entirely instrumental.
I think this makes sense. I hope I conveyed my point.
edit: another note; samples of background noise become very repetitive and annoying after a while, avoid at all costs.