The two main ethnic groups in Indonesia are the Javanese (90 million people, 40% of the population) and the Sundanese (36 million people, 15.5% of the population). Both have distinct traditions, languages, cultures and cuisines. Javanese live mostly in East Java (Yogyakarta, Surabaya) while Sundanese are from the Bandung region.
In Jakarta, most of the girls you meet will be either Javanese or Sundanese. It is also common to come across Bataknese (Medan), Betawi (pure Jakarta), Indonesian-Chinese, Manadonese (Manado) and Makassarese (Makassar). In Bali, apart from Balinese, you will see more Madurese (Madura) and ethnicities from Eastern Indonesia (Flores, Timur, Maluku).
Most expats don't really care about that and they consider it's pretty much all the same. On the contrary, Indonesians like to point at the differences between the people of each provinces.
They will give specific traits to some ethnicities, negative or positive, and based on these stereotypes they might deem that some mixed "race" couples are not desirable. For instance, a persistent myth among Indonesians is that a couple between a Javanese men and a Sundanese women cannot work well.
For better understanding, let's review what are the stereotypes about the three main Indonesian ethnical groups:
The Sundanese Character:
Sundanese Model Melli Voo
What Indonesians say:
Sundanese are considered soft and easy-going. It is said that due to their welcoming nature, the penetration of Islam among them was faster and easier compared to the Javanese. For this reason, they are overall more religious compared to the Javanese.
Some will say that they lack ambition and they are not willing to live far from their home. One of the consequences is that there are less of them in top jobs and positions. Among ministers or ex-presidents of Indonesia, very few were Sundanese.
Sundanese girls are often called the most beautiful women in Indonesia, mainly because of their lighter skin color.
If you date a Sundanese, you might experience a surge in your monthly expenses. Sundanese girls love to spend on clothes, cellphones, laptops, shoes, beauty products and entertainment. Such gifts are expected as a part of the relationship and it is sometimes hard to know how sincere the love is.
Sundanese girls are sometimes criticized for behaving like divas: High maintenance, spoiled, overly dramatic and proud of their appearance. It seems they are aware of their value and they know how to get the best from it.
About their open mindset, Sundanese are hospitable like anywhere in Indonesia. I didn't notice any differences staying in Bandung or Surabaya. I also don't feel they are less ambitious than other Indonesians.
Regarding the materialistic mindset of Sundanese girls: I found it to be generally true, with several exceptions though. You must differentiate educated girls from Bandung's middle and upper class with countryside girls from Indramayu. Girls from poorer background may be expected by their families to marry with someone who will take care of them. Those girls are usually popular among Indonesian men and expats so they have a wide range of option. Naturally, they will not choose the stingy ones. Beauty in Indonesia often comes with at a price and I've learned to be careful with gorgeous Sundanese. I normally avoid them.
The Javanese Character:
Miss Indonesia 2015 - Maria Harfanti - is Javanese
What Indonesians say:
Javanese are often characterized with the "nrimo" concept of life, which means accepting your fate by seeing the bright side of it. For instance, if you cannot afford a car, you will think that walking keeps you healthy. As a result, Javanese are said to be obedient and submissive. They are also avoiding conflicting situations, preferring to keep their feelings to themselves rather than expressing them.