This day we explored Miami city and Miami Beach. The best part of Miami is that their water in December is much warmer than in California during the summer :) Miami is a big business, financial and cultural center. It also has an international hub airport (I wish I lived close to such airport to be able to travel to different parts of the world :) ). One of the best places to visit in Miami is their Bayfront Park. Beware of any special events there which make parking difficult and expensive.
Miami Beach is located across the Miami City. If is famous for its glamorous South Beach, white sand, lots of restaurants and nightclubs.
Key Biscayne is a nice area. While driving there, you can stop and take some pics of Miami. There are also nice parks and Cape Florida state park.
We then drove to Orlando to sleep there and explore it next morning.