This really depends on how much you wish to convert (I know you've stated this) and how much your bank will charge for using your card in an at the moment abroad. Other point to check is how much your bank will allow you to take out from an ATM in one go or per day.

Yes hoteland airprot exchange rates aren't great when you purchase on the day, but they can be relatively competitive when you pay in advance, at times I've got a better rate than the visa rate I'd get from withdrawing cash.

In SeattleDavid example above, for instance, some online UK travel exchange are offering buy-back at marginally better rate than he is getting from his bank (and without commission or any fees for an amount such as yours).

I'd use a travel money comparison site (try use a US, UK and French one), plumb in your numbers and also ask your bank what their current card withdrawal exchange rate is and go with whatever is the cheapest providing it is convient.