On my various trips I have spent about a year and half in Jakarta and perhaps two months in KL. Of the two, I prefer Jakarta hands down. I find it more interesting and the people more friendly. Lots of great clubs and restaurants make up for lack of cultural and tourist type things to do.
Relative terrorism risk: Jakarta is more likely to have something go boom (perhaps much more as KL just doesn't have any history of that), but the odds of it effecting you are minute. London will see another major attack long before either CGK or KL in my opinion. My sense is that there is a slightly higher level of street crime in Jakarta, but if you are an experienced traveler you should not get into any trouble.
Treatment of Americans: KL - no fuss one way or the other. Jakarta - huge affection for America and American culture, but everybody hates Bush. They do a nice job of distinguishing between the people and the government. I have never had a negative reaction to someone discovering that I am an American, and typically get a very positive reaction.
Jakarta:
- taxis: I use Silver Bird, Express, Blue Bird in that order.
- hotel: depends on what part of town you want to be in, Jakarta is huge compared to KL. The JW Marriott and Ritz are both very nice if you want to be in that part of town, the Grand Hyatt is great if you want to be over there, Dharmawangsa is the best of the group. Maybe $110 a night for all but the Dharmawangsa. One step down gets you into the Mandarin or the Aryaduta (Hyatt) for probably $20 less a night. My favorite is the Grand Hyatt as it is attached to Plaza Indonesia so you have a huge mall and entertainment center just through the lobby.
- things to do: malls, restaurants, drinking.
KL:
- taxis: all ripoffs, all the time (except from the airport but you should take the train from there). Most will not use meters and you will have to negotiate a price before you start.
- hotels: I have stayed at the Marriott and Ritz, prices are comparable, both are nice, but not the best of their brands. You should be able to work a deal for around $100 US per night.
- things to do: take pictures of Petronas Towers, then malls, restaurants, drinking.
Have a good trip, TJ