By Noel Randewich, John McCrank and Alun John SAN FRANCISCO/NEW YORK/LONDON (Reuters) – In the weeks before heading to San Francisco for their vacation this month, Jeff Skipper and his wife Valerie, from the United Kingdom, watched helplessly as the U.S. dollar continued its meteoric rise against the British pound. The sterling/dollar exchange rate – which slumped to a record low this week – has reduced the affordability of the already pricey Golden Gate City for the couple, forcing them to economize on some holiday luxuries. “The exchange rate has been the biggest topic of conversation since …