Home prices fell from January to February in 16 out of 20 markets tracked by the S&P/Case-Shiller Home Price Indices, with nine markets posting new lows for the downturn.Miami (0.6 percent), Phoenix (1.2 percent) and San Diego (0.2 percent) were the only metros to record positive monthly returns, while Dallas was flat.Taken as a whole, the 20-city composite index showed prices down 3.5 percent from a year ago -- a slightly less drastic decline than the 3.9 percent annual deprectiation seen in January, but a new low for the downturn. The 20-city composite puts average U.S. home prices back to where they were in late 2002, down 35 percent from their peak in the summer of 2006. Five markets -- Denver, Detroit, Miami, Minneapolis and Phoenix -- registered positive annual returns, although...