Due solely to knowledge obtained through my Indonesian in-laws, I ate lunch today at Wok Coco in an Anaheim strip mall. You would never know this place has Indonesian food -- the signs and menus outside mention Chinese, Thai and Japanese dishes. From the street, it looks like just another Chinese fast-food joint. But the owners are Indonesian and, if you ask, they'll bring you the Indonesian menu. Only a few of the items include English translations, so you may need to ask.
The best items we had were rendang (beef), kangkung (water spinach), nasi bungkus (leaf-wrapped rice, chicken, beef and egg) and a spicy dish of potatoes, shrimp and peteh (stink beans). We were a little disappointed by the gado gado (an Indonesian salad), which was drowned in peanut sauce. But it was a great meal nevertheless.
221 S. Magnolia Ave., Anaheim
wokcocoanaheim.com (although the site mentions nothing about Indonesian food)