Yes, there are protected waters from Miami to Key Largo
The ICW ends in Key West
There are many anchorages between Miami and Key Largo and a few marinas (Black Point,) but even at displacement speeds you can get from Rickenbacker Causeway in Miami (the last bridge before Biscayne Bay opens up) to Sundowners restaurant in Key Largo for lunch if you leave at sunup.
Which side of the Keys are you interested in? The ICW travels down the bay or "back" side of the Keys. If you want the Oceanside you will still be in the protected water of Hawks Channel, but which path you take will be dictated by where you want to go.
You might find this thread insightful:
Ft Lauderdale to Key West