You should be fine if you take taxis everywhere. I wouldn't suggest negotiating the transit system in KL as the lines don't inter-connect as seamlessly as the maps suggest and the tropical heat and humidity is quite stifling especially during midday.

You should note that even on a Saturday, traffic in KL can get quite bad especially if there's a downpour (which would make an outing to Chinatown/Petaling Street quite wet). But the taxis should be able to find their way around jams. Whatever you do, make sure they turn on their meters when you get in a taxi. If they don't, get off immediately.

As previously suggested, Menara KL/KL Tower is a good place to start to get a fantastic view of the city (go by taxi). The view is far better than the view from the Skybridge of the Twin Towers but you still must go to the Twin Towers area for a look-see. The architecture is quite remarkable. If it rains, you could go to Central Market instead if you want to shop for souvenirs under a covered roof, or stay in Suria KLCC at the base of the Twin Towers. Or you can also wander up to the Sky Bar (it's partially covered) for a jaw-dropping view of the Petronas Twin Towers.

An additional suggestion for a place to go at Suria KLCC for a great sampling of Malaysian food is Madam Kwan's. No view, though, but the food quality is higher than that of the food court itself (which is not shabby either). Prices are also higher but not outrageously so. Or pop in next door to Lai Po Heen at the Mandarin Oriental for good Chinese food in refined elegance with prices to match.

Enjoy my hometown! I was just there last week