Don't know if you're still around, but I wanted to respond. This also may not help you because it is not in LA but in St. Paul, MN. There is a group here called The Rose Ensemble (that I used to and occasionally still do sing with). The specialize in music before 1750. One of the group's CDs is called Slavic Holiday and it is all eastern European music, specifically Polish and Czech. It is all very good stuff, and I can say that because I wasn't on that CD. :) Anyway the group sstill does some of that repertoir and tours arounf the country.

Check out their website. www.roseensemble.org
There are also a couple of sound clips from that and their other CDs available in their on their recording page.

Good luck.
John