TITUSVILLE, Fla. (AP) _ Hotel rooms are overflowing, motor homes are jamming the roadways and business people are laughing all the way to the bank as they hope to welcome up to 1 million visitors for Discovery's launch on Thursday.

''We're looking at megabucks,'' exulted Joe Catrambone, executive vice president of the Titusville Area Chamber of Commerce.

Green bows were on virtually everyone's dress or lapel, in keeping with the Space Coast's ''Green for Shuttle Go'' tourist slogan. Green is appropriate, too, because of the many greenbacks expected to be rung up on cash registers all over Brevard County.

''My business had increased 10 times over the last few months,'' said Mada Davis, owner of a souvenir shop in Cocoa Beach.

Police, county and local officials anticipate one of the biggest launch crowds since the Apollo moon missions and the first shuttle launch in 1981. Some visitor estimates are upwards of 1 million.

While business owners and tourism executives beat the drums welcoming visitors, others are bracing for a traffic nightmare and rushing to set up medical aid stations, portable toilets and temporary food stands.

''Can you imagine about a million people wanting to go to the bathroom at about the same time?'' joked Ralph McMullen, director of the county's Tourist Development Agency.

Brevard County, which prefers the tag ''Space Coast,'' has only 8,300 hotel-motel rooms and some 4,000 campsites, and they were all reported full on Tuesday.

Among those not having to sweat and jostle for viewing spaces along the Indian River banks, at Jetty Point Park or on the NASA causeway will be more than 2,000 special NASA guests who will be ushered to a site on the Space Center grounds. These include at least 50 members of Congress, a Saudi Arabian prince, actor John Travolta, actress Darryl Hannah, a couple of Cabinet members and former astronauts.

The VIPs ''have shown an interest in NASA, and they may ''convey the experience to other people,'' said space agency spokesman Mitch Varnes.

Adding to the throng of big-spending tourists is a record crowd of journalists, many of whom came early and plan to stay late. More than 5,000 requests for credentials were received by NASA, said space agency spokesman Dick Young, and of that about 70 percent were expected to be here.

''The media are spending money everywhere,'' said McMullen.

It's just like old times for some veteran bartenders, said Norman Kolsch, operator of Rainbows bar and restaurant in Cocoa Beach, which is doing a heavy business in a concoction named ''Shuttle Shooters.''

The red, white and blue combination of grenadine, cocoa creme and a mint- flavored blue liqueur is so popular that he's thinking of putting on extra help just to keep up with the demand.

''It's really a big challenge and damn hard work dealing with the big numbers,'' said Catrambone. ''But we'll take it in stride, just like we always do.''

He expects some quarter-million visitors in the immediate area around Titusville, a town of about 43,000. Police Chief Charles Ball expects 100,000 of them to line the banks of the Indian River, which is directly across from the launchpad, about 12 miles away. On Tuesday, cars, motor homes and recreational vehicles were already pulling in to stake out claims for good viewing spots.

In all the hoopla, many residents along the Space Coast were not forgetting the horror of the last launch.

At a special Mass last week, some 250 elementary schoolchildren prayed for a safe mission for Discovery and its five astronauts. Several of the youngsters remembered seeing the Challenger explosion through their school windows on Jan. 28, 1986.

But most were optimistic, reflecting the generally prevailing mood.

''They've had time to fix all those things that were wrong. I'm excited,'' said 9-year-old Jenna Rose.