converting
What I did was to open a off-shore account with HSBC (US dollar current account) put my GBP into the account automatically changed into US dollar at 1.65 , they will give you a US dollar debit card and cheque book. No worries about taking so much money into the US.
There are many high-banks that deal with foreign current account, Barclays, Lloyds, Abbey etc, just ask you bank.
adios