LT wrote:
I'm trying to pre-buy an oyster card before coming to London from the
states. The oystercard.com web site won't let me use my phone number. Can
I just wait until I'm there and buy one at Heathrow?

Yes.

Is there any advantage
to pre-buying it?

Not really.

I'm there for 10 days and the oyster seems like the way
to go, is this correct?

If it's 10 consecutive days, a 7 Day Travelcard may save money, leaving
only 3 days on Pre-Pay.

Neil