The sign in rudimentary English greeting George Bush here today read, "You are mostly welcome, Mr. Vice President."

In fact, the Reagan administration, and Americans in general, are received warmly here in the western Sudan, thanks to prompt and efficient U.S. delivery of food to fend off starvation.

A sophisticated long-distance transportation system is steadily delivering surplus American sorghum and wheat. In the drought-stricken western provinces of Darfur and Kordofan alone, as many as 1.4 million of the 4 million inhabitants are receiving American grain. And the rations are being increased to cover nine days' needs each month, rather than six.

U.S. officials estimate that throughout Sudan, Africa's largest nation, at least a fourth of the 22 million citizens could risk starvation. Their plight thus surpasses the problem of half a million refugees from Ethiopia who have sought asylum in Sudan since last fall.

"American aid came just in time," Fatih Bashir Bushara, the Kordofan governor, told Bush today. "Without this assistance from your administration, our people could hardly have survived."

"The people of this region will never forget what the Americans have done for us," he said. Noting that the California-sized province still faces a shortage of more than 400,000 tons for the remainder of the year, he added, "We hope the outside world will not forget us."

Other donors have lagged far behind the United States. "We'll do our level best to help," Bush replied. He said both the government and private Americans wanted to "hold out our hands and open our hearts to the people of the Sudan," all the more since since this country had taken in so many foreign refugees despite its own tribulations.

Watching the vice president walk through a sandy, windblown camp for 27,000 Sudanese drought victims, the U.S. official instrumental in setting the grain shipments in motion said, "Now, because of his visit, I feel confident of continuing American support."

Eric Witt, 44, an agricultural development officer at the U.S. AID mission in Khartoum in January 1984, was sent to Darfur Province to check the provincial governor's prediction of a serious shortfall in grain production. Witt returned to the capital convinced the situation was serious.

His worst-case projections prompted approval in Washington last July of an initial 82,000-ton shipment of sorghum.

By now, more than 1 million tons of donated U.S. grain are either in Sudan, on the way, or pledged. With the exception of a shipment last January that failed to arrive from Texas on time, the grain pipeline is said to have functioned efficiently.

During a drought in the Sahel sub-Saharan countries 10 years ago, corrupt local officials often diverted aid shipments for their own profit. This time, AID contracted a local trucking firm to deliver the grain from Port Sudan on the Red Sea to 22 district centers as far as 850 miles inland.

A U.S. official pictured it this way: "Imagine shipping food to New York and transporting it to Minneapolis, Chicago and St. Louis when the only two-lane road stops in Pittsburgh."

AID also hired seasoned international professionals to ensure that the grain reached villagers. Despite the existence of this camp and as many as 45,000 refugees in the outskirts of Khartoum, most villagers have been able to remain at home.

A foreign relief worker, referring to the minimal role of the notoriously inefficient Sudanese government, said, "If this is neocolonialism, then make the most of it."

"People realize that foreigners do a better job than their own government would," he added. "Any foreigner visiting a village is automaticaly greeted with aish, meaning grain -- they know it comes from America."