I go to my local pasar pagi (morning markets) once or twice a week for a nasi campur breakfast in a little paper cone or banana leaf packet. This is usually yellow (the best!) or white rice with a campur ('mix') of items on top like shredded chicken, noodles, tempe, vegetables, a boiled egg, and some shaved coconut. The mix will be different at every store. I generally say no to the very spicy sambal, especially at breakfast, but you should try it if you like a bit of a kick.
If you are obsessed with hygiene, maybe give the nasi campur a miss — the store owners mostly use their hands to add the items to your rice... in between handling money. But a few extra antibodies won't kill you, and you're more likely to get sick from tap-washed lettuce in a 5-star hotel. Just get past the hygiene aspect, and you will love this easy and super cheap meal. At my markets, I pay R10,000 for one serve (satu porsi) which is A$1. I also like the sweets lady — also for a dollar you can get a mix of local sweets like lak-lak (tiny pandan pancakes) and kue lumpur (literally mud cake, sort of a thick coconut custard cake), all covered in palm syrup (kinca) and sweet shaved coconut.
There are markets all over Bali and your driver will be able to point the way. In Ubud, Pengosekan road has a small marketplace, as well as Jalan Andong, and of course, the large market in central Ubud is always open, with most of the food stalls disappearing at about 9 am. In the evening, Sayan night markets are fun, and there is a large range of food stalls; just wander around and look at the pictures in front of the stalls for inspiration.
Also in the markets category, Ubud Food Coma is on once a month. Warungs and restaurants from all over Ubud gather in one spot with samples of their food, and there are plenty of items to buy (for eating and for gifts). It's fun, great to hang around and listen to a live band and try out food from different places.
Awesome street food to try:
Satay Ayam (chicken) or Satay Babi (pork): These tasty, caramelly, peanut sauce-covered morsels are grilled over charcoal. You usually get around 10 small satays in a portion for about $1.
Satay Lilit: This is minced chicken and spices squished onto cane skewers and grilled over charcoal.
Bantal: little bamboo packages of steamed, slightly sweetened rice, usually with a bit of banana or jackfruit inside. These are useful to buy and carry around for snacking.
Klepon: sweet glutinous rice with brown sugar inside, rolled and steamed and covered in coconut. The liquified sugar bursts into your mouth!
Wajik: These diamond-shaped sweets are made of sticky rice, palm sugar and coconut milk.
Pisang Goring: Fried banana (and sometimes jackfruit - nangka) is found in literally every warung in Indonesia. At the markets, you will often see the stall owners frying the lightly battered bananas in a hot wok, and you can eat them fresh and hot.
Martabak: Hmmm... I could eat this every day. Except I can't because it's really fattening. The sweet version (martabak manis or teran bulan) is a thick pancakey-type of mixture with baking soda. It's cooked fresh on the griddle where it puffs up with air making it soft and light. It's then smothered with butter and you can choose toppings like condensed milk (susu), kacang (peanuts), coklat (chocolate) and keju (cheese). Yes, cheese! Try it — it's weirdly delicious and used in a lot of Indonesian desserts.
The savoury version (martabak telur) is completely different — a mix of chicken and veggie options with herbs and egg, wrapped in a flaky pastry and fried in oil until golden. Hangover food.
Bakso: You will also see the Bakso man driving a motorbike or pushing a bakso cart, and you can flag him down for a hearty stock with noodles and balls of minced chicken and maybe a soft egg. I prefer a takeaway (Bungkus), as I'm not keen on sipping from the communal bowl.
Soto Ayam: This is a slightly thicker version of Bakso with chicken stock, noodles, shredded chicken, a lightly boiled egg and some veggies and/or tofu.
Rujak: This is a weird but delicious salad-like combo of fruits and vegetables, lightly fried and covered in a slightly spicy palm syrup dressing.
Fruit juices and ices: There will usually be a fruit and juice stand in the night markets for all sorts of freshly squeezed juices. Some of these places will have Es Campur which is mixed fruits and jellies with shaved ice and either sweetened condensed milk or coconut cream.
Babi Guling: I prefer this dish at a warung, but many markets will have a little stall serving the national dish of crispy-skinned, roasted suckling pig with a bit of rice and sambal.