Large red Xs and the painted words, "To Be Demolished" in French greet the casual stroller through the dank and teeming streets of Nylon, the shanty slum area of Douala, Cameroon's commercial capital.

The same bold red marks cover the walls of houses in other slums and old one-story buildings in downtown Douala.

"You are seeing Cameroon in a time of big changes," said Paul Fouda-Anambele, director of press relations for the Information Ministry.

"Over the next two years, Cameroon will be spending $250 million on urban renewal" in Douala and the country's political capital, Yaounde, Fouda-Anambele said.

Slum removal projects and public housing construction are not new in Africa. What is startling is Cameroon's ability to carry them out.

Cameroon can boast of an economy that is more vigorous than that of many other African states whose post-independence development began a decade ahead of Cameroon's.

Observers say that President Ahmadou Ahidjo's "green revolution" with its emphasis on agricultural development is the secret to Cameroon's success.

"The "green revolution" began in 1972 after Ahidjo crushed a 17-year-old leftist guerrilla insurgency that had erupted five years before independence in 1960.

About 80 percent of Cameroon's 7.6 million people earn their living from the land. Cameroon's farmers produce a third of the country's $4.4 billion gross domestic product and bring in 70 percent of its export earnings from cash crops.

Since 2977, Cameroon has been in partnership with the ELF Oil Co. of France and Pecten, a subsidiary of the American Shell Oil Co., to produce modest amounts of oil from offshore drillings. It is the much sought-after low-sulfur "sweet crude" oil that is easily refined.

Last year, the country earned $23 million from oil, a figure that is expected to more than double this year.

Gulf, Mobil and the European gas company Total are exploring in Cameroon for what are described as "commercially exploitable" pools of oil, and Cameroon is building a $307 million oil refinery that will take care of its domestic needs into the 1990s.

Ahidjo has said that oil, however, will remain secondary to agricultural development.

In his 21 years in power first as Cameroon's prime minister and then its president, Ahidjo has followed a moderate nonaligned foreign policy that accepts development aid from any source. Even the People's Republic of China, which backed the guerrilla insurgents in the early 1960s, today is building a dam in Cameroon's arid north and a cultural center atop a hill in the center of Yaounde.

Besides China, Cameroon receives aid from France, its major trading partner; Holland; West Germany; Canada; Saudi Arabia, and the Soviet Union.

Americans annually drink $14 million worth of Cameroon's coffee and cocoa, its two major cash crops. The United States recently signed a $21 million agricultural development aid agreement with Cameroon.

Ahidjo, in part because of domestic political pressures (one-fifth of Cameroon is English-speaking) has maintained his distance from Cameroon's major trade partner and former colonial ruler, France -- unlike most other former French colonies in Africa.

Ahidjo never goes, for example, to Franco-African summits that other French-speaking African leaders attend, although he comes from the French side of the formerly divided Cameroons.

In February, Chase Manhattan's board chairman, David Rockefeller, was treated like a head of state when he arrived in Douala to open the bank's branch, the first American bank to open here.

"Ahidjo stays very flexible when it comes to where money or investment comes from," said a diplomat. "The French tried everything known to man, to keep Chase out. But Ahidjo and Rockefeller had been friendly since the early 1970s and they didn't have a chance."

One of the agricultural economy's drawbacks is its heavy reliance on two major crops, coffee and cocoa. A drop in world market prices in the mid-1970s in both commodities hit Cameroon hard.

Then drought, aging trees, inadequate spraying with pesticides and low government prices paid to farmers precipiated a drastic drop in production. Since the government raised prices last year, cocoa production increased 25 percent and coffee productions rose 11 percent.

Cameroon has made large investments in the development of large-scale farms producing crops such as cotton, tobacco, rubber and tea, in an effort to break loose from its reliance on coffee and cocoa. But these farms are not expected to begin export production until the 1980s.

Inflation caused by the quadrupling of gasoline prices (Cameroon's refinery will not be finished until 1981), large scale agricultural development and the smuggling of its abundant food supply to its food deficient neighbors, has plagued Cameroon since 1974.

Wages have not kept pace with the annual 14 percent inflation figure and Cameroon has an unknown but high unemployment rate, boosted each year as 125,000 young people enter the job market.

Despite these problems, Cameroon enjoys a healthy annual rate of economic growth of between 5 and 6 percent and has an excellent credit rating.

The Cameroonians are waiting to see what the trade mission from the United States, headed by U.N. Ambassador Andrew Young, will bring in the way of expanded trade when it arrives next month.

"We want diversity in our trade links," said government spokesman Fouda-Anambele. "We welcome investment here."

"I hope these guys coming with Young can talk turkey," said one American diplomat, "Because this is what the Cameroonians are looking for."