The JW Marquis is amazing - absolutely beautiful and a short cab ride away from the Port. I just stayed at the Marriott Biscayne Bay for work right next to the Port (because the JW Marquis was too expensive); I was very pleasantly surprised - room was a good size, great view, nice little balcony. The outdoor bar was really nice too. My local colleagues commented that they did not know the hotel would be so nice.
Ditto the JW Marquis!!! Hotel Beux Arts located on the top floors of this hotel (a Marriott boutique style hotel) is even more amazing! Personal service, wonderful breakfast, evening cocktails and appetizers, high tech and spectacular views take this even amazing property to a whole new level (pun intended!). The Biscayne Bay is nice and not as expensive of an option.