Q: What is your best advice on converting currency? Should I do it before leaving the US? When in London where are the best rates available typically?
A: I think the rate sterling to dollars is around 1.85 at the moment, which is better for the pound than it has been for some time. So if you can get a lower rate there, perhaps excahnge some cash before you come over. If not, there are lots of exchange places at the airport, and more throughout central London.
However, many people, myself included, nowdays travel with credit cards with pin numbers so that we can simply withdraw local currency from a cash machine (ATM?). These are all over London and depending on how much your bank charges for the service, might be a good option.