Yes, you can choose which partition to use during the install process. 32 and 64 will quite happily work side by side. Out of interest, why do you want to run both?
You mean a 32-bit OS and a 64-bit OS right? If so then yes, yes you can. Of course, the 32-bit OS is limited to 4GB of usable address space unless it takes advantage of PAT (Linux does if it's enabled).