I was always a keen advocate of this method until our trip last year. The exchange rate was average and a min 2% fee plus a withdrawl fee on all withdrawls. Making it worse is the fact max daily limit abroad is now £250. The fees I paid last year for my withdrawls was crazy.
Personally I would rather take my chance with the island bandits than the thieving financial giants. Took cash on a recent trip, and carried most in my wallet, prob makes a difference when not out in clubs and being sober for the whole week that loss of wallet was not an option!
Have a word with your bank. I have lived outside the USA most have my working life. I talk to my bank and they refund the bank withdraw fees. If not shop for a bank with better treatment.