Going to be visiting KL for the first time then off to Langkawi and back. When we arrive we are staying at the Sheraton Imperial - I am assuming we should take a taxi there rather than the Express train? Is it easy to crab a cab at the airport without being screwed

and how much. We would probably prefer this as we arrive in the evening and will be tired.
We are only spending a Sunday day/evening there then flying out next day to Langkawi. Any feedback on the area for siteseeing/walking on that Sunday and any cheap bars/restaurants near by to just sit on a patio etc., Curious how much a beer is in KL?
We are then heading to Langkawi ( probably take a cab ) then arriving back to KL and staying at the Le Meridien. I understand the Express stops right there so I think we will try the train when we come back. Is it easy to get on the train with one piece of large luggage and carry-on each? When we get to Sentral station is it a simple walk to the Le Meridien and easy to find.
Any suggestions as above for places around the Le Meridien - We will be there for a full two days?
Not familiar with KL or Maylasia so any feedback / tips / anything would be greatly appreciated!