I'm not sure about lakes in Orlando but I'm from Satellite Beach and depending on schedule, you can usually find decent water in the Banana River if your able to pay attention to forecasts and pick a day. It seems that it's almost guaranteed to be windy on the weekends though. My friend has a blue '89 Nautique that you may have seen if you were out in the river at all this summer. Unfortunately we ran into some major engine problems and are looking to get that fixed up eventually. On another note, if your looking for someone to ride with, I'm almost always in the area and would love to get out on the water.
Here is a pic of my buddies boat, we were out there a TON this summer...