'WALL Street and US companies have to go global, or go out of business," says John C. Quinn, chief executive officer of Marinvest Inc.Marinvest, which manages some $2.8 billion in financial assets, is 80 percent owned by Hong Kong-based Wardley Investment Services and 20 percent owned by Marine Midland Bank; both entities are owned by the Hongkong & Shanghai Banking Corporation. Mr. Quinn - who has a long career on Wall Street - recently returned to New York to head Marinvest, after several years in Asia. Quinn is representative of the new breed of Wall Street official: savvy about investments, but an internationalist as much adept at working abroad as within the United States. Quinn has held key positions with Merrill Lynch, Nomura Securities International, Irving Trust Company, Chase Manhattan Bank. He notes that even while the US securities and banking industries have been cutting staff in New York in recent years, the two industries have been expanding abroad, as well as in other parts of the US. Meantime, many overseas banks and securities firms are opening offices in the US, especially in New York, or buying US financial companies. Clearly, US financial firms face tough competition from abroad, particularly Japan. "Wall Street" is no longer just a specific street. It is a symbol for New York, particularly lower Manhattan. "Wall Street," in the age of jet-planes and high-speed computers, also means Tokyo, London, Los Angeles, Chicago, Seattle, Minneapolis - wherever securities can be traded or analyzed. Employment within the Wall Street firms that are members of the New York Stock Exchange (NYSE) is up slightly, to 215,000 at the end of June, according to George Monahan, an official of the Securities Industry Association. Almost 6,000 new workers were added to the payroll during the second quarter of 1991. But the crucial point, Mr. Monahan says, is that almost all of them were hired outside New York State. New York City continues to reel from the big layoffs that occurred on Wall Street in the late 198 0s, following the market crash of October 1987. Currently, major banking and securities firms have offices scattered all over Manhattan. Some of the biggest have headquarters well north of Wall Street, in midtown Manhattan. To really catch the mood of Wall Street, one must travel throughout lower Manhattan. While the NYSE is on Wall Street, the American Stock Exchange is a short walk away, directly behind Trinity Church. And the Federal Reserve Bank of New York, on Liberty Street, has more gold on hand than you could count on a long weekend (See box, right). Ironically, the most famous student of the foibles of Wall Street - the Wall Street Journal - is located not on Wall Street, but over near the Hudson River. Other lower-Manhattan offices include Merrill Lynch, the largest US brokerage house, American Express Company, and Salomon Brothers Inc., which is now caught up in a scandal over illegal bids for US Treasury securities. Finally, the financial area means more than money; it is steeped in popular history. Dutch ladies once walked along "Maiden Lane." Jenny Lind, the "Swedish Nightingale," sang at Battery Park a century ago. Edgar Allan Poe used a real-life Wall Street-linked crime as the basis for "The Mystery of Marie Roget," which he transposed to France. And where better to get a feel for the British colonial period than to take a trip to Fraunce's Tavern, a Georgian-style brick house at Broad and Pearl. Yes, George Wa shington visited there. How about you?