Can I connect a non-apple PC monitor to a MacBook Pro?

Yes.

(100418)

Yes ,first get a DVI or VGA adapter from the Apple Store and plug it into the Thunderbolt connector. And check the Displays preference pane to set location, etc.

Mini-DisplayPort to DVI Adapter – If you have a monitor that supports DVI connections

http://store.apple.com/us/product/MB570Z/B/mini-displayport-to-dvi-adapter?mco=M TA4NDU0ODY

Mini-DisplayPort to VGA Adapter – If your monitor doesn’t support a DVI connection then you don’t have a choice but to tap into the default VGA ports

http://store.apple.com/us/product/MB572Z/B/mini-displayport-to-vga-adapter?mco=M TA4NDU0NjA

It's easier than that. PC monitors are moving away from VGA and DVI, just as the Mac has, so you should not limit yourself to DVI and VGA. Newer PC monitors have DisplayPort, Mini DisplayPort, and HDMI. Just look at the back of the monitor or HDTV (any brand) and see which ports it has, pick the most capable (usually newest) port on there and use a cable that has Mini DisplayPort on the end you will plug into your Mac.

Also be careful if you buy a very high resolution monitor (2560x1440 or higher). If you have one of those, you don't want to use just VGA or DVI at all because they can't handle the resolution. For those monitors you want to connect using dual-link DVI or some form of DisplayPort.

(Macs have been able to connect to non-Apple monitors for about 25 years now.)