TWENTY YEARS AGO, when the idea of a Baja California highway from Tijuana to Cabo San Lucas was a Mexican political football, a hardy traveler told author Joseph Krutch:

"Baja is a splendid example of how much bad roads can do for a country. It must be almost as beautiful now as it was when Cortez saw it in 1533."

That traveler might be surprised today at how little Baja has changed, from a traveler's view, even with its 1,061-mile highway, the Carretera Transpeninsular, which opened in 1974. Oh, the American outdoorsmen and tourists have flocked in, many of them fishermen. More than 100,000 American vehicles traveled the highway in 1977. There are gas stations and comfortable hotels where once there were sand and cactus.

But for the most part the highway --a two-lane, nonshouldered ribbon of asphalt that touches the peninsula's two coasts and splits its deserts and mountains -- appears to have altered Baja's people and land little.

The Baja Highway has opened a new world for American outdoorsmen. All year long the highway carries outdoorsmen bound for:

Saltwater fishing resorts such as Mulege, Loreto, La Paz and Cabo San Lucas, where anglers seek about 25 species of gamefish, as well as streamfishing spots in the Sierra San Pablo Martir range.

Deer, javelina, coyote, bobcat and quail hunting sites in the peninsula's northern mountains, duck and goose areas at San Quintin and dove sites at Baja's tip.

Mountain, desert and beach offroad areas for four-wheel-drive vehicles, dune buggies and dirt bikes.

Dozens of remote, little-used Pacific surfing beaches.

Clear-water lagoons and reefs on both coasts where scuba divers explore, photograph and spear fish.

Whale-watching sites near Guerrero Negro, Bahia San Ignacio and Bahia Magdalena.

Fabulous clam-digging, beach-combing and shell-collecting beaches, particularly at Malarrimo Beach near Guerrero Negro.

To drive the highway is to step back into another time, another culture. For example, San Ignacio remains a charming, sleepy town where men snooze on park benches under century-old Indian laurel trees in a city plaza. The highway, which passes nearby, appears not to have changed this beautiful place.

When the road opened, many of the people of Baja were puzzled at how to deal with the waves of gringos it brought. Author Tom Miller, whose "The Baja Book II" is a popular mile-by-mile travel guide, was talking about this recently. He was a dirt road Baja buff in prehighway days.

"I remember when the road opened a man built a little shop just south of El Rosario. He invested everything he had in fan belts -- hundreds of fan belts. He was ready for business the day the highway opened and of course I doubt if he ever sold one.

"The point is, people down there knew tourism would be good for them economically. But because they'd never been exposed to it in those numbers, they didn't know quite how to go about it.

"I've driven the peninsula before and after the highway and I enjoy Baja much more now. Before, on a 10-day vacation to Guerrero Negro, you'd spend six days driving. Now it's a day and a half."

A Mexican will give you a different view of the highway's effect.

"The highway has changed us in ways we never dreamed of," said Al Vela, who operates a hunting lodge in San Quintin Bay. "Do you realize kids rise their bikes 20 miles to school on the highway now? Before, they just couldn't go. Goods and services move over the highway. The highway has brought electrification.

"Tourism has generated many of these things. But the highway has meant much more to us than simply a road for the tourists."

The Baja Highway can take a driver on a safe, scenic trip through some of the most beautiful land in the Western Hemisphere. The highway also can be dangerous because it winds through some of the most inhospitable, monotonous terrain anywhere. For example, there are a half-dozen absolutely stunning lagoons, on the Sea of Cortez just south of Mulege. And there are the hairpin turns as the highway leaves the coast at Loreto and enters mountain terrain, where you might suddenly encounter a Mexican bus going by with inches to spare.

Some tips for driving the Baja highway:

Don't drive at night. Generally, the road is well maintained. But there are chuckholes, and range cattle often sleep on the warm pavement at night. Another hazard: dogs. Mexico has millions of dogs, and many stray onto the road. Also, dips in the road (identified as "Yados" on road signs) may be a foot deep in water if it has rained recently.

Have a through maintenance check of your vehicle before entering Mexico. Because the highway has no shoulder, a stop to change a tire or replace a fan belt could be perilous.

Keep your gas tank full.Pemex, the government oil company, has numerous gas stations but supplies aren't always dependebadle. In Guerrero Negro one recent day, a two-station town, one station was out of unleaded gas and the other had a torn unleaded pump hose.

Take a roll of paper towels. At a Pemex station a quick window wash isn't automatic.

Be aware of Baja weather, which ranges from 100-degree-plus temperatures to floods that obliterate roads. Rain washed out the highway in two places within a half mile of each other just south of San Quintin last winter. Crews bulldozed detours, but it took a day.

At Maneadero, just south of Ensenada, have your tourist card ready to show to a uniformed man in a kiosk in order to travel below Ensenada.

Photographers should know that the Baja highway is frustratingly short on turnouts, particularly on the scenic gulf coast. With no turnouts or shoulders, it's risky even to slow down. In other words, it's a photographer's delight, but it can be dangerous to take pictures.

The highway is patrolled by bilingual mechanics, the Green Angels, who help motorists with mechanical trouble.

The accommodations are comfortable at the seven government-operated El Presidente hotels (double room: $16.50) on the highway from Ensenada to La Paz. Reservations should be made through the Baja tourism office in San Diego: (800) 542-6028. Caravans of up to 30 or more cars often make the trip. An El Presidente can be full one day, empty the next.

While the El Presidente rooms are comfortable, food quality ranges wildly from horrendous (small, cold lobster) to excellent (huge, barbecued lobster). Better you should eat at the Old Mill Motel (lobster, tacos) at San Quintin, the Marlarrimo restaurant (abalone) at Guerrero Negro and the Las Brisas (sirloin tips) in La Paz.

Baja California is a finger-shaped desert. Its sights are enough to excite even the most widely traveled outdoorsman: the blue, pristine waters of the Sea of Cortez; stretches of desert gardens where the land seems to explode with barrel, cardon (up to 50 feet high), candelabra, cholla, pincushion, elephant tooth and prickly pear cactus; mountain passes south of Loreto so barren they suggest Mars, not Mexico; coveys of fat mountain quail alongside dirt roads in the Sierra San Pedro Martir, and the sight of happy men bringing in fish from the Sea of Cortez.

"Pardon me, Senora, does the parrot speak?" asked the gringo in fractured Spanish.

"Si," the lady replied. "Pancho! Habla!" she shouted, whacking the parrot's cage with her forearm, knocking Pancho off his perch. The bird squawked, then shieked: "Pepe!" The lady smiled, proudly. Pancho, an aging parrot with many gaps in his dusty green plumage, sits sullenly in a cage outside a small pink store (cornerstore: 1916) on the Plaza in San Ignacio. Pancho has been for sale for years.

San Ignacio (4,000) is a come-to-life caricature of a sterotype: the sleepy Mexican village. It's an oasis, almost hidden by trees, approximately in Baja's center.

The streets are paved but an occasional swirl of dust from a nearby canyon blows through the plaza. Most of the small store buildings are brightly colored. The newest appears to be the drug store, built in 1939.

An obese, brown-uniformed policeman crisply directs tourists to parking spaces beside the plaza. Then he resumes snoozing, on a red-and-yellow plaza bench.