US gets ready for John Paul II. PAPAL PREPARATIONS

Not the Super Bowl, not the 1984 world's fair, not Mardi Gras have come close to gathering the crowds that will assemble in New Orleans to see Pope John Paul II this weekend. Much the same is true in each of the nine US cities the Pope visits this trip. Not even a national political convention draws the 21,000 journalists issued press passes for the Papal trip.

So Mayor T. Patton Adams of Columbia, S.C., is cruising the city these last few days before Pope John Paul II shows up Friday, letting businesses know by car phone if their grass needs cutting.

During the five hours Friday afternoon that the Pope is in Columbia, the 120,000-strong population of that up-and-coming Southern city will more than double as the faithful and the curious gather into the largest crowd the state has ever seen.

``This is the most important and historic visit in the history of this city,'' Mayor Adams says. Columbia is but 2 percent Catholic, but the business community is footing the Papal bill for the chance at five hours in the world limelight.

In Miami, the Pope's first stop and the place he meets President Reagan, security is a major concern - $5.5 million worth to state and local agencies.

So the county will have 2,000 police officers on duty, the city more than 1,000. The National Guard will supply 2,400 troops and Florida agencies another 900 officers. These will back up a phalanx of Secret Service agents as well as the Papal Swiss Guards.

Airspace and waterways near the Pope's route will be closed to traffic, not to mention streets. The seawall of the estate where the pontiff meets President Reagan has been searched for explosives. Manholes along the parade route have been searched and welded shut against terrorists. Newspaper boxes and mailboxes have been removed entirely.

Background checks have been run on the 29,000 people, including policemen, who will be within pistol range of the Pope when he is outside his bullet-proof, Mercedes Benz ``Popemobile.''

ABC, CBS, and NBC will open their evening news broadcasts from Miami, but viewers there will not be impressed. Local affiliate stations are pre-empting their networks for saturation live coverage of the 23-hour Miami visit.

The Eternal Word Television Network, a Roman Catholic television station in Birmingham, Ala., has signed up cable systems covering 15 million households to broadcast 13 hours a day of live Pope coverage, offered free.

But the planners did not think of everything. About a million southern Californians are expected to line the Pope's parade route in Los Angeles hours in advance without benefit of portable toilets.