The two things to remember with Hollywood adaptations of stage musicals:
1. They cast a mixture of "singing actors" and "acting singers", instead of casting people who qualify as being a "singer/actor".
2. They cut out songs, for whatever reason.
And these things always p*ss off fans of the original stage version.
I'd say go into the movie blind - then you won't be thinking so much about these changes and might be able to just enjoy the movie as a movie.
If you've never seen "8 1/2" (the movie that "Nine" was based on) then that's even better - because you won't be making the kind of comparisons that practically every film critic and cinephile will be doing
(I'll eat my hat if film critics the world over don't damn this on principle just because it is a remake of a film that is considered a masterpiece of world cinema)