Here's my take on money, reposted from a previous thread.
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For money I take US cash in small bills and (usually) enough local currency to get me started which I save from previous trips or order online and pick up at my bank. Generally you'd be fine with just USD to get from the airport to your 1st destination. I also take American Express travelers checks for backup and for hotels, Spanish schools, dive ops, etc. that allow me to pay that way - I find out in advance; they can be exchanged in banks, too, but not all banks and sort of a pain. Most folks have given them up but they're incredibly convenient for largish tabs at places that take them. Then for the rest I use ATMs as I go; in my experience you get the cash in the local currency and the exchange rate is decent. There are fees involved but that's just a travel expense along with many others; some banks charge more than others. I check out the forums ahead and check with hotel and Spanish school folks once I'm on the ground and avoid ATMs in areas with a history of problems.
A few years ago I set up a travel account at a credit union, separate from where I normally do my banking; ATM card use is free and they reimburse foreign fees as mentioned above. I use it while traveling, then change my password and empty it so I don't have worries about subsequent removal of the funds if the ATMs are buggy - often the fraudulent withdrawals are made months after the trip. I have it set up with daily emailed balance notices so I can keep an eye on my balance without having to use my bank password in questionable wifi environments. I have a newish travel credit card from Bank of America, too - no foreign transaction or ATM fees.
I set up my accounts to be notified by email when there are deductions (in case of fraud) and when my balances get to a certain level; I can transfer money between accounts online but only do it from secured wifi.
I only go out with the amount of money I need, sometimes in a 'throw down' wallet with a few expired cards and the day's cash. If I am transitioning from 1 place to another I keep my passport, cash, cards, etc. under my clothes.
Be sure any US (or other foreign) bills you bring are in very good condition - no tears or pen marks on them. The banks are getting increasingly picky about accepting bills like that so providers are generally careful to check and will reject imperfect bills. Also at least some banks in Guatemala will only exchange $50 and $100 bills now, not $20s.
One of my best tricks to avoid handling a lot of cash as I travel is to deal with really reputable hotels and transport providers and make larger payments before I travel. For me this is mainly with folks I use trip after trip and really trust so isn't something that works for everyone.
Remember to notify your bank and card company you'll be using the cards on foreign shores - where and when - and also find out before you hand over your card if there will be an additional fee for charge card use - sometimes 5% or more. I email myself a scan of the travelers check numbers and our main passport pages and pack a copy of them with me, too. I also go to http://www.oanda.com/currency/travel-exchange-rates and make tiny cheat sheets with the conversion rates for each country to keep handy. Happy trails!