Yes, the partition will be bootable, but the drive may not be. It depends on what you do to the drive in the meanwhile. Specifically, the first sector or so holds the master boot record and parition table. If these get altered (if, say, the drive gets formated) then they would need to be rewritten before the computer will boot.
The following is the basic command to back them up and restore them. You will need to make sure how much needs to be backed up though (I'm guessing just the first sector)
dd if=/dev/hda of=MyBackupFile bs=512 count=1
dd if=MyBackupFile of=/dev/hda bs=512 count=1
In other words, disk dump from the primary master hard drive (hda, notice no number trailing) into a file; transfer 512 bytes at a time, 1 time. If I'm wrong on the size you may not get everything, so be aware...
On the other hand, if you do nothing to alter the MBR etc, then yes, the partition will boot just fine. If you ever lose the MBR, then there are places in this forum where you can get help.