rEFInd is an EFI boot manager. As such, it installs as files in the EFI System Partition (ESP) or in the main OS X partition; it doesn't write anything to the MBR.
You don't say if you're setting up a dual-boot installation or replacing OS X with Debian, thus creating a pure-Linux setup. If the latter, my recommendation is to use MBR partitioning rather than GPT partitioning and install the BIOS version of GRUB (or LILO or SYSLINUX, if you prefer). The Mac will then boot using its BIOS compatibility layer, and you'll be able to treat the computer like a standard BIOS-based PC. Doing a Linux-only EFI-mode installation is tricky because Apple's EFI implementation is weird and doesn't work with the usual Linux tools for manipulating EFI boot loaders, such as
efibootmgr. Although it's possible to do the job with tools like
bless (a more-limited implementation of an OS X tool of the same name), this process is poorly documented, and I doubt if the Debian installer supports it directly (although I might be wrong, especially for Debian 7).
If you're doing a dual-boot installation, I recommend you install rEFInd in OS X. Installing to the main OS X partition tends to produce fewer problems than installing to the ESP, although installing to the ESP is necessary in some cases. Install the EFI filesystem driver for whatever filesystem holds your Linux kernels, too, and if you use a separate
/boot partition in Linux, be sure to create a
refind_linux.conf file in the directory that holds your Linux kernels. This is all described in the rEFInd documentation.