Help with weeds in landscaping?

 
Hi all,

Anyone know how to keep down or get rid of the crown vetch and dandelions
that keep coming up through my junipers?  

I have a pretty large hillside that I covered with plastic & mulch...  cut
holes in the plastic to plant blue rug junipers, but I keeps getting weeds
- I think some are coming up though the holes I cut & others are growing
out of the mulch.

I'm hoping theres a spray that will kill the weeds, but not the junipers!

Here's a couple of pics of whats going on...

http://img210.imageshack.us/img210/23/hill2vd4.jpg
http://img210.imageshack.us/img210/3904/hill1qs7.jpg

Thanks!