U-Haul says people are on the move again and they are headed for Idaho.   The City of Boise has become one of the nation's most popular destinations for people on the move.  An annual migration report by U-Haul International Inc. shows that Boise was the nation's second-highest "growth city" in 2010.  The Phoenix-based moving company's report compared rates of people moving in and out of cities. Boise posted an 11 percent inbound migration rate, second only to the 20 percent inbound rate for Santa Monica, Calif.  The Ada County Association of Realtors attributes the growth rate to Boise's affordability and quality of life.  The Idaho Business Review reports that U-Haul's migration study included cities with a population of at least 5,000 and is based on data from more than 1.4 million U-Haul one-way truck transactions.