I had read about this place on happycow, and here's my Swinger's Diner review. I've only eaten here twice, both times with friends, including non-vegetarians. They seemed to like it just fine.
It's diner style food and decor with booth seating and bar seating. The decor is interesting and colorful, a bit retro.
For vegans and vegetarians there are wraps, a couple sandwiches, and usually a vegan soup. I think the food was decent but not memorable. Oh, I hear that they sometimes offer a vegan cinnamon roll (haven't been back to try it though). With so many pure vegetarian and vegan choices in Santa Monica, Swingers is just not on my list of go-to. But it's veg friendly enough and you can come with non-veg friends.