Hey, me and my band want to record a rehearsal, and I need help.

I was just thinking of bringing my pc over, attaching the mic and hitting record.

Will this work?

Or shall we do individual recordings of the instrument and mix it with a software?

Some advice?

We don't want a super high quality demo or anything, just something audible to listen to on our own accord (we've tried with mobile phones but...eeew).

Thanks in advance.
Never imagine yourself not to be otherwise than what it might appear to others that what you were or might have been was not otherwise than what you had been would have appeared to them to be otherwise
It certainly will work, however, if you can use more mics on individual instruments and mix them down that will sound better.
I record my bands rehearsal all the time. I use my SM57 plugged into my lexicon interface and adjust the level so it doesn't clip. I use cubase to record on and just adjust the mic position in the room so i can hear all the intruments decently. We only use the recording as reference and it gets the job done. Cheapest way to go. Best of luck.