We are Canadian but vacationing in Mexico, so yes we did exactly that. We had to pay duty in Mexico when it arrived, but all enTourage needs is a US address. We happen to use myus.com but any service like that should work.
Our credit cards are Canadian, so we didn't have that problem (just weren't actually home when the thing would be shipped) but I can't imagine a foreign credit card would be a problem - credit cards are generally accepted everywhere, at crappy exchange rates, but it should work.
And yes, I registered when I received it here in Mexico, and to my knowledge, nothing went wrong.