I got married on the Carnival Liberty in the Port of Miami last May. Most of us flew in and we trying not to have rental cars, so I did my research to find a nice affordable hotel with entertainment and restaurants nearby, that also had transportation to the port.
We stayed at the Holiday Inn - Port of Miami, Downtown and LOVED IT!!! Very affordable hotel that is directly across the street from Bayside Marketplace.
The Holiday Inn was just as any other Holiday Inn is...a clean and well kept mid-grade hotel. You can request a room on the front of the building overlooking the bay, which we had and loved as we were able to watch the ship come into port the night before. You could see the lights of Bayside, all the cruise ships and Miami Beach. SO PRETTY! (If the lights aren't your thing, don't worry there are thick curtains ;) There is no continental breakfast but rather a restaurant in the bottom. The outdoor pool was very clean and enclosed by a concrete wall for added privacy and security which turned out to be very nice for those corraling small children and a favorite of my wedding party. The staff is courteous and the concierge can really provide! Though a free shuttle to the port is not provided, the concierge will arrange for a shuttle for your group (ours was $5 a person) no matter how big or small to make it to the port. Our shuttle came with an enclosed trailer behind for luggage which was extra nice! I HIGHLY recommend this hotel for its courteous staff, conveinence to shopping and dining, and cost!
Bayside Marketplace is an outdoor mall with local vendors as well as chain stores and several restaurants and a food court. You can also board a tour of the bay or Millionaires Island from Bayside. There are bands playing in a courtyard area in the evening and it is patrolled by officers, so it is much safer than walking the streets of downtown Miami. Please check out their website which has a list of stores and restaurants. I really can not describe how conveinent, fun and perfect Bayside's proximity was for us travelers without cars.