I'd say try whatever you like, you're bound to learn something, even if that's that you prefer Ubuntu! I found my favourite distro starting out was openSUSE, mainly because most things 'just worked' on my hardware at the time (Dell inspiron 5100 laptop). If bandwidth isn't an issue, I quite often download a whole bunch of live CDs and see what's changed in various distros I like; Ubuntu, suse, sabayon, gentoo to name a few.
As for the 64-bit thing, installing a 32-bit OS won't cause you any problems (you no doubt had 32-bit windows..?). If you want a 64-bit OS then the confusingly named amd-64 downloads are the ones you want, often named (less confusingly) x86_64. (amd-64 is the architecture in Core 2 processors, so named because amd invented it)
Last edited by mmatt; 07-20-2009 at 12:04 PM.