Miami has something for everyone. Beautiful weather, beautiful beaches, great food and lots of attractions. In March Miami, especially Miami beach, is pretty much taken over by Spring-breakers. There's nothing like 100's of college kids packed into a few square miles of sunny beaches, all drinking and hitting the bars to the wee hours of the morning. Of course- you should really only go during that March/Easter time period if you are into the spring break thing. If you want a family vacation, selecting another month might be advisable.
In addition to drinking the delicious margaritas and strawberry daiquiris that dot the beachfront bars, there's plenty of other fun stuff to do at the beach as well. If you are willing to pay a bit more, you can rent a boat and go out for a great sale or a dinner cruise. You can also go jet skiing in Biscayne Bay, which isn't too expensive for a good hour of jet ski fun. There are also spots for windsurfing- although its harder then it looks because that sail gets heavy in the water. Make sure there's enough wind before you try out that adventure- but not too much for beginners.
There are plenty of other attractions for spring breakers besides the beautiful beaches and great bars. Miami has a fun zoo, which is a great way to kill an afternoon if you get tired of the beach. You can visit the monkeys, and see some of Florida's famous alligators. This would also be a fun family activity to do, if you decide to come to Miami outside of the crazy spring break season.
If you get bored with the great outdoors, Miami also has wonderful shopping and restaurants. Be sure to hit up one of the great outlet malls- they have great deals on more expensive stuff like Coach or Ralph Lauren, but there are also less expensive outlets as well. There are a bunch of different outlets, so be sure to ask at your hotel for directions to the one closest to you.
There's also great dining in Miami. Go to one of the cute little beachside bars for cheap seafood that you can eat right out of big baskets- or pay a little more and go to one of Miami's many fine dining establishments.
Overall Miami is a great place to visit. Its hot, but with a balmy ocean breeze.
Quick Tips:
Make sure you to Miami Beach- the famous area for parties and celebrities. It lives up to its reputation- especially around Spring break time. Lots of beautiful mansions, celebrity style houses. Lots of spring breakers. Lots of beachside bars and dining places. The sand is beautiful, the surf is great, and its just a great place to be.
Check out the Miami zoo if you like that kind of thing- they have a great alligator world where you almost feel like you are seeing them in their natural habitat. The monkey house isn't bad either.
Rent some jet skis on Biscayne Bay. You can rent by the hour and its not that expensive. Its a great way to go out and get in the water and experience the surf. They are fun and you can go fast and race and there is enough waves that it gives you a ride that is an adventure!
While you are at Biscayne Bay, go a little further up to the tip (further south from Miami beach) and see the Cape Florida Lighthouse. This was a great working lighthouse on the tip of the gulf but it has now been turned into a museum and it has some great nautical history as well as a very nice view of the water that you can take pictures from.
You can also visit Everglades National Park in Miami if you are into nature. They rent bikes or you can take one of the nature hikes. I'd recommend renting a bike- you get to see more of the beautiful park without getting tired from walking. The bike paths are beautiful and well maintained and the park is a haven in the middle of the Miami Beach craziness. There are lots of beautiful plants and flowers and you may even get to see some of natures creatures in their natural habitat.
Although your hotel will probably have a pool, the Venetian Public Pool is worth a visit. It used to be a rock quarry, but now it is a beautiful and well appointed public pool with a grotto and waterfalls carved from the original rock. Unless your hotel pool is very nice, this one will probably be nicer, and it is neat because it incorporates some elements of real nature- its not just artificial.
Also, you probably want to check out one of Miami's great outlet malls.Best Way To Get Around:
The best way to get around, by far, is to rent a car. While they have a bus and a metro system it really only serves the city center and will not get you around to the zoo or to the lighthouse or to the shopping districts, an it may not be convenient to take from your hotel to the beaches. It also stops running earlier than the bars close, which can be a drag.
If you rent a car it is not hard to get around. Remember though, if you are under 25 you have to pay an additional fee to rent a car. But once you do, the roads are pretty easy- there are not a lot of those confusing one ways to make you lose your way. There is, however, a fair amount of traffic so be prepared to be patient if need be. I'd recommend renting a convertible so you can experience the balmy Florida breezes as you drive around town in style.