There are a lot of misconceptions about Travelers Checks. Yes they still work, no they are not a big hassle, just a small hassle like everything else these days. HOWEVER most people don't know "how they work".
Asking to "cash" a travelers check will almost always get you a firm "no". Businesses don't want to cash your checks when you are doing zero business with them.
If you want to convert a travelers check to cash, just wait until you need to BUY something. You can spend $5 and pay for it with a $50 travelers check and you get the $45 change back in cash.
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For RVing you really need everything... credit cards, debit cards, checks and cash.
While society is trying to force us away from cash and insisting we give out our phone or email just to make a simple cash transaction, cash still works but merchants seem to prefer anything they can track you with, such as debit cards, credit cards and store accounts.
Ironically, I've run into some small bargain campgrounds that took only cash and nothing else. Ditto for some mobile repair men. Perhaps the owner is a bad manager or they're trying to fly under the radar of past liens or taxes, who knows, but it's a reality that still exists now and then. Some businesses only deal in cash, period.
In the event of a disaster though, cash is king. When supplies are premium, power lines are down, the merchants revert to cash only. Been there, done that, and it wasn't pretty. Those with cash could obtain provisions, those without, did without.
You can have a bloody fortune in the banks and perfect credit with a plethora of cards, but it will get you nowhere when the local economy temporarily goes cash only and supplies are far and few. This can happen after an earthquake, flood or even a hurricane or ice storm that wasn't suppose to hit your area. You may need help, Good Samaritans are in short supply, but cash can often persuade instant help for sure.
Cash is also good to have if you end up in the middle of nowhere and you've done something silly like get your RV or car stuck in the muck out of cell phone range near a lonely road of virtually no traffic. The farmer 3 miles away might use his tractor to pull you out for free, then again, he may be a very busy man and you're just not on his list of charity work to do that day. Cash compensation can get that tractor moving pretty darn quick.
Many disasters can not be planned for, but having been through my share, both with and without cash, it's an absolute nightmare not to have any cash around should you suddenly find yourself in the midst of a catastrophe or just a boo-boo in the middle of nowhere.
It makes smart sense to have a fire and water proof safe in your RV for computer backups, important papers (like your insurance policy), your address/phone book backup, spare credit cards and some cash if you so desire. Heaven forbid if you're in a fire or accident, there's a good chance your safe contents will survive. It's very cheap insurance for a one time purchase.
SentrySafe F2300 Fire-Safe Waterproof Chest
http://www.amazon.com/gp/product/B00006IBHM/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B00006IBHM&linkCode=as2&tag=recreationalvehicles-20