What am I supposed to say?

On my way home from the store a lil while ago I got pulled over by 2 Mormons on bicycles. They said the whole bit about the book of Mormon and do I want one and all the stuff that goes with it. But I'm a strong christian on my way to school in Portland and I serve a lot in my church, however when I talk to these people I always seem to be at a loss for words. Now I want to be nice to them I don't want to just blow them off. I find that I end up hastily running some banter how I'm such a good Christain (I Go to church! Serve all the time!) and I realize afterward it just makes me look like a self-rightious oph and it doesn't bring glory to God. Furthermore, when I went to shake his hand, he said that his name was El Dorado ( Now this is an awesome name but no one in their right mind would just name their kid that). Now do the Mormons get new names or "Spiritual names" When they go on their missions? Whats up? Now I know where my faith lies and its not in a religion but a relationship. I just want to know what I should be doing in these kinds of situations. To bring glory to God.