The nice thing about KL is that it's the home base for Air Asia, so there are dirt-cheap flights to anywhere in Asia, most of which (Indonesia, Thailand, Vietnam, India, southern China) can be reached in under 4 hours by plane.
There are downsides to KL, but in my opinion its not either of those.
House prices - Not according to https://www.propertyguru.com.my, I looked up Cyberjaya as an example (~15mins on train to KL sentral) and freehold $120,000usd for a 4bedroom/2bathroom place, 1 bedroom condo for much less. That would buy you half a car parking place in Hong Kong (on leasehold no less). Regardless you'd just rent anyway, at least for first few years, $300-$400pm for a nice serviced condo with pool/gym. No point buying unless you eventually get a permanent residence.
English language - I never had a problem with English in KL or Penang or even Alor Setar, except maybe one of the old roadside tea vendors, but that's probably my northern accent. It might not be Singapore or HKG level but it aint significantly off.
Cyberjaya is like the upcoming tech scene of KL imo. It has a growing number co-working spaces, plenty of decent accommodation for low prices, hosts many of big data centers including IBM, doesn't suffer from the traffic issues of the center, parks and greenery, air feels clean, is 15minutes from airport or 15mintues to KL sentral via the train etc.. I usually stay Citadines at DPulze which puts you pretty central and above a shopping centre, it's quite sparse so you'll need to GrabTaxi to different co-working places etc... If by action you mean nightlife it's meh, there a little pretend irish pub where locals smoke inside and few other sterile hiso venues, better hit Bukit Bintang if you need a beer or three (happy hour trend is 3x for some odd reason).
