In general, Miami Beach is very safe. As my colleague below suggested, South Beach is great. You may get little more for your money in some other locations, it really is about the lifestyle you are looking for and your budget.
I work in the Miami Beach area, and also am very familiar with Sunny Isles, Bal Harbour, Surfside and North Beach, all of which could be great options.
I would be glad to assist or answer any questions.
Feel free to search my company web-site below, you can see which areas and buildings you may like.
I look forward to assisting you!
South Florida Brokers