I think a lot depends on how you plan to pay for what. We use credit cards for everything that we can, and only use cash if credit cards aren't accepted at a business or if the credit card systems are down. Because of that, we bring $50s and $100s, and generally only use about half of the cash we bring. The current exchange rate isn't that high, so we don't concern ourselves with 1:1. We also bring a stack of $5s to tip our housekeeper each day.

And to repeat what has been said, we always bring at least three different credit cards, just in case.