I had read about this place on happycow, and have eaten here several times over the years. Was just here in late November 2012, here's my Interim Cafe updated review.
I appreciate that this cafe, while not all vegetarian, offers many vegetarian and vegan options, and it also uses some organic ingredients.
The prices are typical-affordable for a lunch casual place in Santa Monica. The selections are varied: organic hot oats, tofu cancun, gado gado, maui veggie burger, vegan mac & cheese, BBQ drumstix, tamales, baked goods, and organic coffee.
Small space, relaxed mood, with indoor and outdoor seating. When the Chef and owner Eddie is around, the atmosphere enlivens and the food usually is better.
They currently serve a vegan chocolate soft serve. It's good but a bit too sweet for my liking. I would recommend one of the burgers or salads. The tamale, though, is not quite as good as it could be--has too many different herbs, and the mixed grains that comes on the side is hard to chew (needs to soak grains in water, or cook longer).
Interim Cafe is a decent place to grab lunch or a coffee when in the downtown Santa Monica area.