The sunrise is beautiful here. I usually end up somewhere the vicinity of 8th and 14th. But it really doesn't matter, no matter where you land you will see a spectacular sunrise.
I will say that March in Miami is a joy weather-wise. And as long as you are luky enough to have some clouds, and there almost always clouds, you will get a truly breath taking sunrise.
Depending on the morning, it could get cold/breezy since even though it isn't too cold. It can still be cold if you know what I mean. As a counter to that you will also some mosquito repellant just in case the bugs decide to come out for a bite. They usually get hungry around dawn.
As for sunsets, they can be a whole lot tricker and are more dependent on where you are. One place, The Flamingo on the beach has some really nice sunsets. While a sunrise is almost a sure thing sunsets are really iffy. By the way, if you happen to be feel like a good samaritan, pick up some trash, people can get careless with their trash on the beach sometimes. While there are often organized community trash sweepings initiaives they aren't enough and it always helps if we make an extra effort when we can.