At least on Linux Mint Petra the mount of an SD card will not survive suspend mode.
My basic idea was to replace the USB stick with my personal data by an SD card, which fits even better into the hull of my notebook than a nano-sized stick, but while the USB stick survives suspend quite stable (only with rare exceptions), the mount of the SD card is lost every time.
So I am back to a nano USB stick.
Looking around this seems related to the Kernel Configuration Setting for
CONFIG_MMC_UNSAFE_RESUME, which is not set on Ubuntu and Mint, and there are
reasons for this (race conditions during resume).