Re: Should we mix or not ?
If you like the music typical for more than one style of dance, you'll probably like mixing them. If you don't, you probably won't.
Re: Should we mix or not ?
My view is, um, it depends.
If the question is "Should people (as individuals) dance whatever form they want", then I'd say yes, absolutely. Dance to the music, and to your ability. If a WCS-able track comes on, and your partner is happy to do WCS, then why now? Similiarly for cha-cha, nuevo tango, and so on.
If the question is "Should there be an official mix?" - that is, a room designated as "Swing / MJ" or whatever - then I'd say no, definitely not. Simply because these rooms, in my experience, tend not to work - too much faffing around deciding whether you're a swinger or a jiver, etc.