SteelBird
Colonel
Most merchants in East/SE Asia don't accept USD directly, you must go to money changer to convert to local currency first. I travel to Asia 2-3 times/year. There are countries that use USD as legal tender, like Panama. Tourist trap locations are also more likely to take USD currency.
Never change your USD at the airport, except for a small amount to pay for taxi and tip. You get much better rates at money changers in the malls.
The above statement is completely wrong for Cambodia (as a SE Asia country). Well, we are the country that welcome USD the most! You can use the USD even for filling station, taxi or buying a cigarette without loosing any value at all. The smallest change we accept is $1, if you buy things which cost less than a dollar, you'll get your change in local currency (Khmer Riel). In the capital of Cambodia, Phnom Penh, people have USD in their pocket more than Khmer Riel. Most imported merchandise are sold in USD. If you go to a super market all price tags are in USD!!! You might ask me "why?". Well, but that's a matter of fact. The people used to have no confidence in local currency, longer and longer it becomes a habit. I used to make a joke like this: "the East uses Vietnamese Dong, the West uses Thai Batt and the Central uses US Dollar". You might ask me again, "So, where do people use Khmer Riel?", the answer is "Khmer Riels are for local products and small changes". Poor Cambodia!!!