There's a big problem with _any_ Ranma / Romeo and Juliet combinations of
this sort:

Ranma and Akane do _not_ fall in love at first sight.

They're far to similar in certain respects to get along well initially.

As for this _particular_ idea:

For one thing, the Puerto Rican girls shouldn't be considered part of the
'Sharks' gang.  They're just girlfriends of the gang's members.

How in the _world_ would you do the fight scenes?!?!  I can't think of
anything more opposite than how these two stories treat fights.  Ranma's
fights range from silly to serious, but WSS is _choreographed_ for
goodness' sake!

Personally, I don't see these two stories fitting all that well together.
Having most of the Puerto Rican girls be fighters and fall for Ranma would
be stretching the original WSS too far.  On the other hand, Ranma not
having a number of violent girls after him is stretching too far in the
other direction.  I'm not saying it can't or shouldn't be done, but I have
the feeling that you're going to have trouble making sure that you simply
don't repeat "West Side Story" with character names from "Ranma 1/2."

Why Ranma at all?  I can think of a half-dozen better Animes off the top 
of my head to cross with "West Side Story."  Anything from "Ah!  My
Goddess!" to "Urusei Yatsura" would produce fresher ideas and make for a
better story.  The characters of R1/2 are too dissimilar to the ones
from WSS to make a good fusion, but at the same time they aren't
dissimilar _enough_ to make a good parody out of the idea.

I admit that "Ranma 1/2" is popular and easy to write about, but there are
times when it just doesn't work!

---------------------------------------------------------------------------
    Josh Green, aka Pi -- SORT@BUCKET.UALR.EDU
       http://bucket.ualr.edu/~sort/fanfic/
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(Egad!  I must really not like this idea... not a single one of my stupid
jokes in the reply.)

P.S. If banning movie x-over idea posts would eliminate this kind of
thing, I think I'm for it.  (Speaking as a person who recently posted the
spammy "Adventures of Ranma Munchausen.")