Malls and "non-pro" students
"Three nuts" - sorry for delay in posting in reply to your question, I've been working in UAE where I can't get access to this site.
Firstly, I have hunted in Mangga Dua malls; it's quite different from the more upmarket malls (PI, PS, Senayan City etc) in that the girls in this area are much less experienced in being approached by men (especially bules). It's not like other low end malls where there is an obvious "market" - I'm thinking of Atrium in particular which you should try if you haven't already. The consequences are that there is much less chance of them speaking English - in fact I've picked up maybe a dozen girls in Mangga Dua (over a VERY long period of time) and none spoke English at all. Also - and I've found this - you can pick a girl up and go for coffee with her as a preamble to taking her back to your hotel but she may well have no idea at the outset that this is just a precurser to sex. When she realises she will be off. Not there will be a problem or "scene", but it will be a waste of time.
As for non-pro students - the best time/place is Ciputra Mall late afternoon. It is close to Tarumanagara and Trisakti Universities; loads of girls wander in at that time. Not far from there is Slipi - a small mall which is also very good - maybe better - but is very popular with local business men doing the same as you and frankly a lot more experienced and quicker of the mark than you or me. The biggest mall of the lot is Mall Taman Anggrek which is also close by, I've found it not quite so good as the other two, maybe because it's so big but it's worth a try.
You can see all these malls which are on your right as you drive from the airport to the city, roughly half way. Trisakti University is on your left opposite Ciputra.
There are low end bars with "massage" in this area as well - I've posted on them as have others if you want to search the forum. In summary, I wouldn't recommend them and the area can be slightly worrying after dark if you are not familiar with Jakarta. I have wandered around that area myself however and never had any problem at all.