I loved South Beach when I stayed there in November. We had no problems, just take normal precautions and you should be fine.
I wish we had googled more things to do before we went though. Someone told me not to miss the Blue Martini Bar...except we did

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Everyone there raved about South Beach. We stayed over one street from where you are, which was right across from the beach. Lots of neat hotels and such.
It's really pretty