The Winter Park chain is a great place to ride. I grew up there and spent almost every afternoon out on Lake Virginia. There are actually two public boat ramps that are easily accessible. The one on Lake Virginia was already mentioned, but there is another one on Lake Maitland at the Fort Maitland Park. I guess it just depends on which boat ramp you live closest to. These are both public ramps, but Winter Park/Maitland requires you to purchase a registration decal to use the chain (or you can just purchase day passes). If marine patrol catches you without this, then they will probably fine you. However, in the past they would only come out on the weekends. I'm not really sure what its like now, but I rarely saw them during the week while I was growing up. Another thing to consider with the cops in Orlando is that they really do know what's going on with regards to USCG approved vests and excessive ballast in your boat. They will give you a ticket for riding with a non-CGA vest and they are starting to question boaters about how much weight they are running in their boats (this happened to me the last time I was stopped). I just wanted to give you a heads up, so you aren't caught off guard.
If you have any other questions about the Winter Park chain or any of the other lakes in the area, I'd be more than willing to help you out. Welcome to Orlando!