score:2
The express train from the airport KLIA Ekspres has free on-board WiFi - which is actually quite reasonable (in terms of speed), but so is the train so by the time you settle in the train is already at the station.
Most of the major shopping complexes near Bukit Bintang (like Berjaya Times Square and Low Yat) offer free wifi (some, only if you are a customer).
Almost all the coffee shops and fast food places have wifi (by mandate of the Kuala Lumpur Local Council), but most will only give you the password once you buy something.
I don't recall having wifi at the metro stops though.
You can also subscribe to data-only plans from the major providers; you'll find excellent 4G coverage across the KL and uniform 3G service if you plan to travel through the country.
To get a SIM card, you'll need to bring your passport and there are kisoks available at the airport.
Call rates are quite reasonable and coverage is also excellent; however you won't need the data if you are spending the majority of your time in downtown KL as there is plenty of WiFi available.
Maxis, Digi and Yes are the three major players (Yes being the newest).