Having been raised- mostly- southern baptist, but with a very open mind in my household, I feel that, no matter who you are and what you practice, if you find yourself in a ritual or ceremony or congregation of any religion, respect that tradition's practice and faith by joining in. It would be both a learning experience for you, and a new way to celebrate the One, because it doesn't matter what path you choose in life, all paths end with the One.

Saying this, when I do attend church services with my family (which I have to admit I rather dislike) I join in- I know the songs and I know how I'm supposed to act, but I always keep in mind and heart that I have chosen a different path, and I recite that in my mind when the preacher prays.