We chanced upon Cafe Warung Murah in Seminyak when we were trolling the main strip for something to eat, something more local and less sterile than most of the fancy restaurants.
Here, the atmosphere is like a kopitiam. The food was authentic and we ordered dishes that were cooked to order. The prices were reasonable and relatively inexpensive - think 3 dishes, 3 drinks cost us around S$16 in total, and the portions are hearty even for 3 (we were 2 people eating).
For the budget conscious, there is also a selection of precooked dishes that you could pick from, not different from our local "economic rice".
Tuna satay. Meaty and spiced like otah. Delicious.
Gado Gado, a vegetarian's dream loaded with tons of different greens and a creamy peanut sauce that also packs a bit of heat. The sauce made the dish really substantial.
You should also try the avocado shake while you are in Indonesia. A local specialty, the subtle green and buttery flavor from the avocado blended with ice is a really delightful treat in the hot weather.