I'd find it very difficult to date/be with someone religious and NOT attend important religious events. I am lucky in that I've got a very hippy religion, and all of my dates have not been very religious. But to me:
Short term: If you knew nothing about it already, I'd go for courtesy but make it very clear that I do not subscribe to this, I already have a firmly rooted belief elsewhere, and that while I enjoy learning what helps you and makes happy.. it is not what works for me.
It isn't like going to church is going to convert you or anything. I've been many, many times, and actually had fun and enjoyed it all. It was fine. It isn't what I believe necessarily, but it is a holy place of worship and it can have a very positive atmosphere. I think everyone benefits from being around people that are happy and energetic about something.
Long term: That requires a bit of sitting down and discussing.. especially if kids are involved. It's always nice to be able to bridge gaps in beliefs, and I think many, many people end up adopting some form of beliefs from one another as a general principle of growing closer together. But it's an important aspect to look at--marriage, children, and how stressful situations and deaths in families are handled rely heavily on religious views.