I've never been to Miami as an adult , so since we wanted to do a (precruise) day of sightseeing , I was in the same boat as you re / hotel . After looking at alot of posts at cruisecritic.com re / miami hotels . And going to travel and hotel websites . I ( now having an idea about costs ) went lastly to AAA south auto club that Ibelong to and found some , called a few , and at last made a good deal and set a reservation . Good luck , it takes some research .
I booked a room at Best Western Marina park with a view of the harbor so we can watch the Explorer sail in on Sat. a.m. Booked directly with the hotel as this was the only way I could get a room with a view of the harbor. The rate was 80.00 plus tax for 3 adults and a baby, so your rate may be lower. The hotel has a web site with photos and claim to be the closest hotel to the port of Miami.
if price is a primary cosideration consider priceline. Go to: www.biddingfortravel.com for info. I bid $30 4* Miami downtown and got the Hyatt Regency . There is a $5.95n booking fee and taxes are extra so my pre-cruise nite for 11/16 comes to $40.