How do you know that they hire 300 indonesians? Have you read it somewhere? Its standard practice for the last 3 years, girls are hired just before Hadj on a short term contract which is then extended.
Saudi Arabia is a strict Moslem country, therefore the dress code applies to everyone. The idea of wearing an Abaya shouldnt be a deciding factor, it must be worn in public but not in any housing compound or beach facility, in these places your skimpy dresses would be a must!
Some people can tolerate the place and even enjoy it, others find it to be an earthly replica of hell............. you will only find out which category you fall into after you get there!
Good Luck.
Mutt.