California exports to Mexico surged 25% to $5.2 billion in the first half of 1997, offsetting steep declines in the state's shipments to Japan and South Korea, the office of Gov. Pete Wilson said. Overall, California's exports edged up 2.1% to $53 billion from January through June compared with the same period last year. It was the second straight year of sharp first-half increases in exports to Mexico as that nation's economy continues to recover. But shipments fell by 9% to Japan and 18% to South Korea, which the state blamed on the appreciation of the dollar against those countries' currencies. Exports to China rose 11%; to Hong Kong, 20%. High-tech industries accounted for 72% of the state's exports.