I talked to a pair of Mormon missionaries in the town my mother lives in a year or two back (Sister Sarah and Sister...Whitney, if I remember correctly?). They were very nice and quite respectful and accepting when I told them that I'm already quite committed to the Episcopal Church and sincerely doubt that will change, and I took some literature from them as a courtesy.
Sorry, I don't really have much more to add to this conversation.
I had the same situation happen to me at school a couple quarters back.
While I don't care much for the content of their doctrine, and they seem rather paradoxical in the way they seem to be almost arbitrarily conservative on some social matters and not so much on others (from a Catholic's perspective), for example on birth control/condoms, I have never once had a bad experience with a Mormon. I have never met an unkind one, and Washington has a fair few of them. I admire a lot about them sociologically and find their geographic and historical attributes fascinating. I really like that they're generally anti-alcohol, etc (though I personally couldn't live without caffeine and won't be converting any time soon).
From what I've seen, a lot of Mormons tend to have a common physical and physiological appearance to them. They aren't the only smallish conservative religious group where this is the case, but I've noticed it most often with Mormons. I can't quite describe what it is, but my Mormon-dar is pretty strong. 
Actually, Mormons tend to frown on birth control unless it's between a married couple.
And yeah, I've noticed that non-Mormons who know Mormons frequently say that Mormons tend to have a common physical appearance; that could be due to the extremely white skin color of most Mormons combined with the non-usage of alcohol. Of course, then they meet the Polynesian Mormons and that tends to throw off the Mormon-dar. 
Seeing that the Mormon settlement in Utah happened with a mix of 19th century White former Protestant American (before the South European immigration to USA) and North European converts and mostly grew afterward through high birth rate, it's not surprising that Utah Mormons are lighter than the average White American.
