My BF lives and rides in Miami. Our favorite ride goes through Coconut Grove, down Bayshore Drive and then out to Key Biscayne -- all the way out to Bill Baggs park. There are wide shoulders and TONS of cyclists doing that route, so cars are used to seeing bikes. On the way back from Key Biscayne, turn into Virginia Key park (free for bikes) for another few miles and another chance to see the ocean.