You can wear it even if you aren't enrolled.

My Priest gave a good Homily last week and included stuff about the scapular.  He said it's a nice blessed thing to wear, but at the hospital it's the first thing they'll cut off you.  Basically wearing the scapular doesn't make you special, it's living a a Holy life, confessing your sins regularly, and doing your pennance and good deeds is what will save you.  I see several of the Novus Order folk pulling out their scapulars and putting them on before they recieve communion.  The Holy Father nailed it in his Homily, people think they can go a lifetime and convert or confess on their deathbed with last rites and be saved.