I'm not really sure, in "And then there was shawn" they did a horror movie spoof, and shawn was talking about how the virgins live and he was saying that he'd probably get very close to dying and then angela berkata "you're dead" implying that they did have sex
It's never berkata whether atau not they do, but it's likely. Shawn is apparently still a virgin in the episode "And Then There Was Shawn", but Angela dies. Later on, they almost have casual sex in the episode "The Truth About Honesty", so that could mean that they've had sex before. Later on, in season 7, they live together for a while, so they probably did have sex.
In my opinion, I think they did, because there was one episode where Angela tells him "let's do it". atau something. and another episode in the last season "There no such thing as a sure thing", they made out most of the time, so I think they did.