Places to hike in Malaysia and its neighbors

Hi,
This is a pretty open-ended question; I'm hoping to get suggestions.

I'll be in Malaysia next month, May 2012, for a couple weeks on business, but I'm planning to take off a week and explore the region before my meetings start. Never been to Asia, so this is a first. I would love to find a place where good hiking is accessible, and I'm wondering if Thorn Tree members have recommendations for the best place to go.

My preferences:
-I like to hike alone if possible, which is to say I don't want to be tied down to a big group of slow walkers who want to stop for pictures and souvenirs every hour. I understand that guides are common here, and I'm not allergic to them, so if I could find a small group of similarly-minded people to split a guide with, that would be fine.
-I'm not planning to bring very specialized equipment, since the focus of my trip is supposedly business, but I've got good boots and a big backpack, and I could probably borrow a sleeping bag.
-Ideal would be day-hiking from a central point where I could crash at night. I'm also OK with an overnight or two, but this isn't a long backpacking trip.
-My location restrictions: pretty broad, essentially anywhere within a cheap AirAsia flight of KL. Cheap meaning $<200, I think.
-Budget: I'd prefer to spend less than say $300 on guides and accommodation during this time. Is this reasonable?

Candidates:
-Mount Kinabalu, Sabah: sounds amazing, but also expensive and bureaucratic. I'd be hiking around May 22 or so, which might even be booked now.
-Cameron Highlands: It's unclear how good this is for hiking, or if it's just little nature trails and such.
-Bako national park in Sarawak: Sounds very jungle-adventurous, and I found a post indicating that guides are the exception and not the rule here.

I would welcome any additions; I don't really know the country that well and am probably unaware of lots of stuff.