Highdesert, glad to hear you'll be spending a couple of days in my hometown! I don't live there now but I still feel the love! The suggestions thrown out so far all sound pretty good to me. Here are some additions:
It's good that you've decided to stay near the airport on the night of your arrival in Malaysia. The last run to town on the KLIA Ekspres departs at 1230a so you wouldn't even catch that after clearing customs. There should be options to fit most budgets, including Tune which begins operations in the KLIA vicinity this year. However, you might want to splurge a little to recover from the long flight! You'll find that rates in Malaysia will seem low to US travellers, even at the more upmarket chains.
On your return to LCCT, I should say the best option would be to take a taxi or shuttle bus to KLIA and get on the KLIA Ekspres there. Based on your arrival time, you would be heading into town right about rush hour. Taking a taxi might seem convenient but you will almost certainly get caught in rush hour traffic, which is BRUTAL. Any savings you'd see in taking the bus from LCCT into town would be negated for the same reason, plus the buses make several stops along the way. Honestly, KL rush hour traffic is no laughing matter.
The shuttles departing LCCT for KLIA are less than a 5 minute walk from the LCCT entrance. Just ask at the information counter for where to go, and double check with the driver to make sure you're boarding the right bus (green Cityliner). One caution: you will have to lug your bags onto the bus as they don't stow luggage under the bus carriage. No biggie, really. I did it and and helped a friend with her THREE bags, and it was fine. Just a heads-up, that's all. If all goes well, this will get simpler in late 2011 when they install the proposed rail link between LCCT and KLIA. Fingers crossed!
For shuttle bus info, scroll to the bottom of the page:
KLIA International Airport - LCC Terminal - getting to terminal
The Cityliner shuttle costs only RM 1.50 (under USD 0.50). The ride to KLIA is about 20 minutes so don't worry if it seems to take longer than it should. At KLIA you will save a little if you buy a return ticket on the Ekspres.
If you're dead set on taking a taxi pre-pay at one of the cab counters and forego the 'luxury' cabs. Sure you'll be riding in a Mercedes or something similar, but it costs a good bit more.
In KL, staying around Bukit Bintang means you'll be in an upmarket area with lots of ex-pats and tourists. Nice hotels, shopping and restaurants/clubs. I 100% agree that you should eat in Jalan Alor! The old shophouses are also quite pretty. FYI, the city council may have renamed the street (stoopid!) but Jalan Alor is well-known and locals will be able to point you in the right direction. And just about everyone is friendly to tourists. Malaysians are friendly people!
The other option mentioned was staying near KL Sentral. Le Meridien and Hilton have hotels right next to the train hub. Just for a frame of reference, a regular room at the Meridien is about RM 390 + tax (just over USD 100, quite a bargain). From KL Sentral you'll be within steps of the LRT, Monorail and KLIA Ekspres. To see the Petronas Towers, you can hop on the LRT right there. Typically, I wouldn't recommend staying by a transit hub, but Sentral is actually well-maintained and nice! And since you won't be in town long, the convenience factor cannot be overlooked.
Kuala Lumpur Hotel: Le Meridien Kuala Lumpur--Hotel Rooms at lemeridien.com/kualalumpur
Hilton Kuala Lumpur hotel
A short walk from Sentral is the Little India area around Jalan Brickfields. If I'm not mistaken, Deepavali (Festival of Lights) falls sometime in October, so the area should be quite festive. You'll be close to good Indian food. Actually, ask around for the 'chee cheong fun' cart near the YMCA (open only at night). It's a Chinese dish of steamed flat rice noodles served with veggies stuffed with fishcake. You'll eat it standing by the side of the road but that's one authentic Malaysian experience under your belt! There's also a night market in that area, but I've forgotten which night.
A short cab ride away is the Royal Lake Gardens, which is quite pleasant in the late afternoon when the sun is not so strong.
Sorry about the long post. I got carried away! You really won't go wrong with the others' advice. And as Wisnu said, if you take the necessary safety precautions and are mindful of your surroundings all will be well. Hey, we divers are all about safety first anyway, right?
Happy diving, and I hope you enjoy your time in KL!
