A few thoughts:
Have 2 debit cards, use separate pins on each card, as others have pointed out best of on 2 different networks. Keep them in separate places - i.e. not both in your wallet!
-one of these cards should be the Charles Schwab card for all of the reasons mentioned above
-perhaps the other one could be from your high interest account (unless you don't want to have access to all of your savings via a debit card in case of theft). Would be nice if it were also a no foreign transaction fee/ATM fee reimbursed card.
-set your high interest account to auto transfer every 1-2 weeks your budgeted amount into Schwab; then you only have to make extra transfers when something out of the ordinary happens.
-have a "cushion" in your schwab account in case you miscalculate something.
-consider adding an authorized user in the states that you trust, consider giving them online access to your accounts to they can watch for anything strange from home.
Have at least 2 credit cards with no foreign transaction fee, again, don't keep in the same place... Visa and MasterCard have the widest acceptance. CapitalOne cards all carry no annual fee and no international transaction fee.
Consider this one, a straight up 1.5% cashback everywhere with no annual fee and no FTF is not too shabby. A number of other cards have no international transaction fees, such as the
Priority Club Visa and the
Marriott Visa - both of these cards have hefty signup bonuses and earn a free night certificate offsetting the annual fee (waived for the first year) as well, so if you're going to be staying at hotels at all along the way, they may be good options. Discover Cards also carry no annual fee or foreign transaction fee, but are not as widely accepted.
-Autopay is your friend.
This table has a ton of information regarding debit/credit cards for international use.
As others have mentioned, carry some cash to get you through in a pinch. Not a great amount, as cash obviously cannot be replaced when stolen. Again, don't keep it all in one place. Honestly, when accepted you're much better off using credit/debit cards...they can be replaced if lost or stolen
However, in my experience, getting them to remote areas in 3rd world countries is NOT easy at all.
Try to avoid changing money (cash) as much as possible...it's a wripoff. Remember with Schwab, you can make small withdrawals for no penalty/cost...which means there is no advantage to carrying a lot of cash. Best if you spend most of the cash you get in each country...
US dollars will be accepted in a lot of places, and sometimes it won't cost you more to spend them - my rule of thumb, always pay in the currency quoted (be it USD or local currency). If they convert, even into their home currency, they usually use a rate that is favorable to them, and sometimes by several percent.
Travelers Checks? They're a thing of the past, but I carry some just in case...to get me out of a pinch. They're nice because they are replaceable if lost or stolen, so you can afford to carry a bit more. Banks almost everywhere will take them, even if for a hefty commission.
Keep all of the NON toll free numbers for your banks/credit/debit cards in one place. Might be best to only write down the last 4 digits of the credit/debit card numbers on this paper, and keep 2 copies. Last 4 digits because into the wrong hands your cc# can become a nice tool...DON'T carry a copy of front and back of all cards as some may recommend - it includes your ccv code...Usually with the last 4 numbers and other identifiers, the bank can look up your info, but then you're not handing out your account numbers to anyone who gets ahold of the paper.
Toll free numbers are HARD to call from abroad - but, you can use gmail or skype. Again, the local "call me collect" number is best.
Get a cheap Quad Band unlocked GSM phone (should be able to get one for $20 or so); or if you are a T-mobile or ATT customer and already have a quad band phone, get the unlock code from them while you're still a customer in good standing. It is incredibly cheap to get a SIM card in most countries, and usually surprisingly cheap to call back to the states. May help you in an emergency...may help you get ahold of your bank quickly (program your bank phone numbers here?)... Even if you don't plan to be using it frequently, may give loved ones at home peace of mind that they have a way to contact you... FORGET using your US based cell phone abroad, it is incredibly expensive.
Get an iPod touch or other similar handheld wifi enabled device (or old wifi enabled smartphone) - there is wifi everywhere...
Watch your credit card and bank statements closely. Fraud, while quite uncommon, is easily remedied if caught in time.
Carry extra copies of your passport everywhere. Go to Kinkos and get 2-3 wallet sized color laminated copies made (photo page on front, signature page on back). This will suffice as ID many many places worldwide (i.e. Hotels, not immigration), and prevent you from having to produce your real passport except when absolutely necessary (so that you can avoid unnecessary lost or stolen risk).
Consider an annual medical evacuation insurance plan. I have one through travelguard (~$200/year); however, I believe it only covers me for trips of <90 days, so you'd have to get a policy to cover what you are doing. Get one with high benefit limits...medical evacuation costs a TON (hundreds of thousands is not unheard of). Consider having emergency medical coverage as well.
Have fun...if you need any tips on Central America, most of my recent travel is there.