I think your garage would be fine (no light in the fridge after the door is closed either). My garage does not have enough light for normal plant growth. There is a small window which allows me to see, but as far as a plant is concerned it is dark. They do fine. Like I said, I leave them outside until a hard freeze threatens and then bring them in the garage for the winter.
Generally, don't cut anything off that is still green. I cut my plants back now (Feb or March), just removing brown sections and dead leaves etc. They will begin growing in April.
Interesting thing about the dark, cool garage. I also keep a couple "tropicals" in there that would normally want full sun, like a potted lemon tree. My house has limited sunny windows. Warmth plus darkness is bad, as they try to actively grow but don't have enough sun to do so. The lemon generally lost nearly all it's leaves by Spring (but would recover over summer). The last two years I have also kept it in the dark garage. Because it is cool, it has stayed green and healthy.