I found the ATM is the "best"...gives out the day's rate...are either $20 or $50 bills...is good any time day or night (nothing like getting $800 @ 3am, lol)...all for the cheap price of $1.50-$2.00.
But stay away from strip clubs ATM, those can charge more. A big name bank ATM seems the best and watch out were you are at....3am I am at the casino not the street ATM. (doesn't mean you have to spend it at the casino, ha ha)