Yup, I have been there many times.  The LA branch 
is pretty much liked the other stores in Japan.  
They carry some rare and good cels in the 
showcases.  And tons of junk cels spread around 
into different baskets.  They carry at least two 
thousand cels there, so I'm sure you will find at 
least one or two cels that you like.  Even if you 
don't find the cel that you like, I'm sure you can 
always find something else to buy, because they 
carry tons of manga, artbook, doujinshi, toys, CD, 
posters, pencil boards and many other 
merchandises.  Mandarake is the best anime store 
in LA, and probably the best in the US, you have 
to visit at least one time :)