hi brainmonster, before you buy the b/w film .. do you have a lab that will process it for you ? some labs that do color processing will NOT develop black and white film, it is a completely different process to get the film to convert to negatives .. that is, with the exception of the xp2super already mentioned. color film is either c4t1 ( color print film[including xp2]) or e6 which are slides/positives. both of those types of color films ( c41+e6 ) are their own process too, and a lot of regular labs won't process e6 film either so make sure if you buy color film to shoot you get c41 color NEGATIVE film. with regards to converting it to b/w post processing, you can do that no worries and make beautiful images ( also mentioned ). in the end often times its the image that's important, and no necessarily how you got there. if you are getting your feet wet, i'd just grab some cheep consumer c41 color film and convert it like you planned. if you have a friend or lab that will develop your b/w for you and you want to try it to see the difference in "image quality" definately check it out ... there are differences in the tonality and how the image looks that might be considered subtle but they are there.
have fun !
john