If you're talking about privilege as in saying their sexuality is not subject to careless generalizations, mockery and stereotyping, then yes. Even though that has more to do with LGBT discrimination than any reputation hetero people may have.
I don't think it's a privilege in the same way as white privilege, which is more of a (sometimes subconscious) casual feeling of security towards white people and insecurity towards people of other races (and even people within those races are guilty of this).
Unless it's obvious you're gay, people do assume that you are straight all the time.