Loan to Mexico Is Part of Wise US Investment The author of the opinion-page article ''The Holes in Mexico's Bucket,'' Aug. 9, seems to lament the fact that the United States continues to be involved with and committed to Mexico, questioning the validity of the US loan and loan-guarantee package. US business operations in Mexico make US firms more productive and more competitive worldwide. Greater success in international markets means more jobs in the United States. Despite the serious crisis in Mexico this year, Mexico is expected to purchase more than $40 billion worth of goods from the US - more than any country except Canada and Japan. US direct investment in Mexico - plants, factories, manufacturing, and service operations - amounts to more than $30 billion. US businesses have played an active role in Mexico for more than a century and are indeed stationed here for the long term. While economic downturns are unwelcome, there are strategies to deal with them. President Clinton's emergency-aid package, extended to Mexico in its hour of need, was the act of a friend and a neighbor, but it was coupled with a direct economic benefit to the United States. The Mexican government has indicated that it may not need the entire amount originally agreed upon in the loan package. Mexican leaders have taken many difficult steps necessary to accelerate recovery. And positive economic signs, such as a dramatic drop in interest rates, are already evident. Advocating a more prosperous Mexico via the loan-package agreement is among the better investments the US can make. Those who choose to disagree with this should, at minimum, double-check their ''facts.'' Ollie J. Akel Mexico City President, Exxon Mexicana Ripken's silent message I have just looked at the cartoon ''Move Over Cal Ripken,'' Sept. 7. The cartoonist, in condemning recognition of Mr. Ripken's accomplishment, evidently believes that we who celebrate it are somehow heartlessly forgetting those who toil every day out of the public spotlight. The truth is completely to the contrary. Sports, at its best, serves as a metaphor for success and failure in ''the real world.'' Cal Ripken, because of his status as a major league ballplayer, is recognized all over the country. When he shows up for 2,131 consecutive working days and when he works through injury and fatigue without making excuses, he honors those of us who do the same things in our less-than-public lives. He tells us, without saying a word, that we, too, are heroes. Mark S. Humphreys Sierra Madre, Calif.