Hey man,
There is never any reason to turn down an opportunity to record something.
I meet with people to make sure it will be cool for THEM to record with me, rather than if its cool for me.
I have always recorded everything I could possibly record and mix. Sometimes you will find that you learn more than you thought you would learn in a session that is outside of your normal thing.
Don't forget that you are allowed to have your own personal tastes, but they don't really matter when you are the producer or the engineer. You need to do your job and make it great and appropriate to the genre you are working on. It is not about whether you normally listen to hip hop or metal or hardcore or folk or cumbia or whatever... It's about making a great record.
Professionals know that making a record sometimes has very little to do with making music.
The more you record, the better you are at it. That's a constant truth.