I had read about this place on happycow, and here's my Nature's Grill review.
Was here on a Friday during lunchtime, in February 2012, and the restaurant was quite busy. Seems like a popular place with the locals. The menu is very vegetarian and vegan friendly. Some of the vegetarian items can be made vegan by requesting substitutes (soy cheese, vegan mayonaise).
My husband and I share a soup & 1/2 sandwich combo and ask for vegan mayonaise on the bread, which they offered at no extra charge. We also got the tempeh tacos. Both plates were served with a side of blue tortilla chips and salsa.
Overall, the food was good enough, not fancy, but tasted healthy and clean - simple American California fare.
Nature's Grill has a string of locations up and down California. See their website info.