I'd ask first yes,but you never know.
I love it, absolutely love it. My g/f and I share our 'juices'. She loves to do oral after we've had sex, to taste us together, and then kiss me to share the tastes. Or she'll share my semen after I come in her mouth. It just depends on the guy.
As far as I'm concerned, I don't expect her to do anything I won't do- i.e. I don't expect her to swallow if I wouldn't swallow it, etc.