Would like to add Insulation?

Would like to add insulation to the attic and would like to know if it's worth doing? I live in Florida and I was told I have R19 in there now. Electric company did an audit and said that I could use another R19 to bring the total to R38. The neighbors said that I am wasting my money doing this. Will adding this insulation keep the house cooler in summer and warmer in winter and is it worth doing?