yeah u can be friends with them. just like the-prodical-son said, only take advice from Christians. theres a lot of kind non-christians. im a christian and i have non-christians friends. i avoid to go out with them to some places becoz as a christian my place is not there. the gud thing in this is u, as a christian, will b there to tell them about Jesus Christ, about God, invite them to go to the church with u some day, give them godly advices.
im sure dat a christian's life can bring a non-christian to want to know God. but u just need to always remember dat u r christian, ur following the gud path, keep acting like a christian in everything, say NO to things dat would not please God, and by the love u have 4 ur friends, tell them about Jesus Christ, AND through ur life, make them scream "theres a God", make them scream "God exists"