Spanish Bank Courts Hispanic Customers in United States
Spain's Banco Bilbao Vizcaya Argentaria will buy south Texas banking group Laredo National Bancshares, heating up race by global banks to serve Hispanics living in US; Banco Bilbao says $850 million purchase will give it access to potential market of some five million Hispanics in south Texas; Banco Bilbao's chairman-chief executive Francisco Gonzalez comments; photos (M)