>I would like to start using Less CSS pre-compiler (after reading about it online). But then I read that in order to use Less with VS 2012 you need to install Web Essentials 2012. And then I read (in comments) that Web Essentials will not work with VS 2012 Web Express (which I have). Can I still use LESS without Web Essentials?

I would have thought so. Web Essentials might give you better intellisense and automatic compile but those not be 'essential' :-}
You could still compile manually (or use the httphandler)
Disclaimer : just a guess - haven't tried it....