Not completely sure about CSA, but I would imagine it would be similar to our experience at CN last year. The church shuttle was listed on the activity sheet, we met in the lobby, and the driver gave us the choice of the Catholic service or the "gospel" service. We went to the gospel service and it was our favorite part of the whole trip!
They are very used to tourists and most of the tourists sit in the balcony at the top. The driver told us what time to be outside for pick-up. (which was before the service was over.)
If it isn't on the activity sheet, I would just ask at the front desk, I'm sure they could assist in arranging something. It was a great experience, I highly recommend it.
I didn't see this thread come up until I had already posted mine on the 15th. I too, had asked about church services. We will be at CSA the first week in June and would love to go to a gospel service. Going to a "Gospel " service in Jamaica would be soooo awesome. Hopefully they will have a shuttle bus that will take us and a group that is going. That would just be great!! I know it would be a "Blessing"