First of all, I'm not a vegetarian, but I LOVE Zen Gardens. Whenever I want to have a "veggie day", I would come here. The food is definitely good enough to convince meat eaters to eat with you here without feeling too hipster (not that that's a bad thing really...) Even now, I'm sometimes amazed at how they make the mock meat look so real and taste so good!
What you MUST order (or in my opinion, the best thing on their menu): ENOKI MUSHROOM BALLS. It is this savoury fried crispy thing that is as addicting as chips... so yummy.
Even though it's a franchise, neither the atmosphere or food seems like it. Prices are pretty reasonable, and generally the food is quite good. Bento boxes seem to be popular at this restaurant. Also, they have authentic imported teas in which they sometimes have tea ceremonies...?
If you've never tried a vegetarian restaurant, you should definitely try this place (regardless if you're an omnivore or not).