HI renee,
You should find a big difference for one thing you will be with normal people ,well when I say normal you will meet the odd eccentric but they will be human unlike the JWs'.The congregation will be full of people for the most part who are there with a loving caring attitude.Of course there will be cliques and a bit of rivalry sometimes the same as you get in all walks of life but the act of coming together to worship in a church as apposed to a meeting in a sales enviroment will be uplifting.You should enjoy the fellowship and not take things too seriously . The way children are treated is totally different to the Jdubs way of doing things,the mainstream churches involve the children in a way that will make them interested in the being there you also get to say things like Happy Christmas, and have a lovely Easter and Peace be with you.
And by the way taking communion will be something you will want to do regulary once you progress within the church,Don't be put off if anything seems a bit strange or if someone seems a bit off hand, give it time and you will feel the spiritual benefit.They have great hymns to sing as well and a very important part of it all is that you will make a lot of new friends,and I mean real friends not at all like the ones at the KH.
Peace be with you.