Along the main street of this little Napa Valley town, signs in front of the sweet shop and service station urge residents to "Save Calistoga," as if the old community, famed as a resort in the last century, were facing some sort of dire invasion.

What the signs are seeking protection from is something called "Calistoga Falls," a proposed "world class" spa with a 400-unit hotel, a conference center, restaurants, cocktail lounges, tennis courts, swimming pool and a man-made waterfall, which its developers say will flow across part of the lobby.

In some ways the battle over this planned $24-million hotel complex is like countless others that have been waged over development projects around the country. Proponents of the resort facility argue that its completion would help revitalize the town by pouring tax funds into coffers depleted by Proposition 13. Opponents contend the project would be an incongruous blot upon the local landscape, destructive to the rural character of the place and its surroundings.

But the debate over the Calistoga spa is part of a much broader dispute -- one that concerns the future of the entire Napa Valley, and with it the fate of a major resource for California and the nation.

The valley has long been recognized as one of the world's premier wine-growing areas and particularly in the last decade its products have outscored some of the fabled wines around the globe in blind tastings. Even the French have found it wise to establish wineries in the Napa Valley and there has been a rush by foreign companies to buy up available wineries in the area.

At the same time, the valley has become a major tourist draw. California's entire wine country is ranked by some measures second only to Disneyland among the state's attractions. More than 1.5 million outsiders visit the Napa Valley annually on one mission or another -- sampling the wines, soaking up the rustic culture of the vineyards and the wineries, or merely basking in the clear air and gentle beauty of the countryside.

Moreover, increasings of those visitors are staying. Even as the nation has discovered California wine, it is learning that the region where much of that wine is produced is one of America's most pleasant places to live.

The 35-mile-long Napa Valley lies like a green oasis an hour's drive from San Francisco, and it has drawn a rising tide of those able to pay the soaring price of its land. The influx has included movie producer-director Francis Ford Coppola, socialite Pat Montandon and author Alex Haley and his children. A home and 213.6 acres recently were acquired for $3 million, reportedly as a hideaway for rock star Rod Stewart.

In the past, all three of these principal users of the valley -- winemakers, tourists and exurbanites -- have coexisted here more or less cordially. The tourists, besides bringing money, have helped promote the image of California winemaking to the nation and the world. And the homeowners have added to the tax base while generally occupying land that is not particularly well-suited to grape growing.

Now, however, this once-easy balance is threatened. Some Napa residents believe that their valley's very success has prepared a path to its possible destruction by luring more tourist and residential development than the region can handle without losing its principal function -- that of growing, harvesting and processing grapes.

To prevent that loss, some residents are mounting vigorous campaigns aimed at mobilizing such traditional weapons against development as zoning strictures, environmental impact requirements and planning documents. But some believe that local approach will not be enough. They have begun lining up support in Washington for a remedy that they suggest may be unprecedented: declaring the entire valley a national park or federal preserve, to protect what they consider a national treasure -- the wines of the Napa Valley.

"I would rather keep the federal government out of it and depend on the county, but that may not be possible," says Bernard Skoda, owner of the Rutherford Vintners winery and a leader in the successful fight 20 years ago to prevent a six-lane freeway through the valley.

The idea of a national park or preserve for the Napa Valley is not new. In fact, it is in some ways just an expansion of an existing agricultural preserve voted 11 years ago by Napa County's board of supervisors.

Under the rules of the preserve, a house may not be built on any parcel of land less than 40 acres in size either within the preserve itself (basically, the floor of the valley) or in the watershed and transition areas surrounding it. In addition, by agreeing to certain conditions for a 10-year period, a winemaker gains the right to pay property taxes at favorable agricultural rates, instead of as a business.

The trouble with the county system, some in the wine industry fear, is that it is vulnerable to a very slight shift in the political winds. The five supervisors often split 3 to 2 in favor of steps to preserve the area's agricultural character: the change of a single vote thus could turn that majority around.

The advantage of a federal preserve, proponents argue, is that, once granted it would be unlikely to be altered or abolished. But obtaining the preserve, winemen concede, will take considerable effort.

"People in the wine industry are used to waiting and they have learned to prepare well in advance," says Michael Mondavi, president of the Robert Mondavi Winery in Oamville, who recently discussed the plan with members of the California congressional delegation in Washington. "It takes seven years to plant vines, have them mature, then age the wines before you can sell a bottle." It will take the same kind of patient effort to win federal help for the valley, he argued.

The vintners' principal fear is that real estate developers will simply be able to outbid them for land, and that the influx of residents will dislodge them from power in local government bodies. This is a general fear in any wine-growing area and it is sufficiently severe for the Wine Institute, the industry trade association based in San Francisco, to form a committee to study the prospects for a battle between wine and real-estate interests over land and water.

Meanwhile, the Napa supervisors voted recently to lift the minimum purchase in the preserve and watershed areas to 40 acres from 20. And the Napa City Council has rejected a proposal by Amfac Corp., the big development company based in Hawaii, to build an additional 600 homes and condominiums at its Silverado County Country Club. Instead, the council allowed Amfac to build only 26 units.

To Napa real estate man Skee Lisle, all this smacks of excessive caution and control. "The way it is now, none but the rich can buy in the valley," he contended. "There is plenty of space in the hills that is no good for grapes. Why can't they ease the heavy zoning in those areas?"

At least one winery owner, Louis Martini, who has lived in the valley most of his life, is sympathetic to Lisle's view. Some of the people who have moved into the valley in recent years, he complained, are among those calling loudest for limitations on further development. "Heck," he said, "If they want to take that attitude, I could say I would like to have seen it shut off in 1933."

But to Napa County planning manager James Hickey, at least some tight limits are needed. He, along with many other valley old-timers and county officials, hopes to confine the main tide of newcomers to a few towns -- Napa at the south end of the valley, and by far its largest community; Calistoga at the northern end; and Rutherford, St. Helena and touristy Yountville in between. "Even here, extra people mean extra (government) services and taxes, and I'm not sure we're prepared for that," Hickey said.

The increase in newcomers has been large enough already to provoke some friction between farm and residential factions. The farmers say the newcomers are complaining of noise from machines that scare off birds from the grapes, of traffic on the highway during the harvest being slowed by gondolas (carts filled with grapes), about the noise of sprinklers used for frost protection at night as well as the use of water for this purpose during times of shortages. They complain too, say the winemen, of the spraying of the vines and the noise of mechanical harvesters that can pick grapes at night when they are cool.

The farmers maintain there is nothing to complain of about the spraying because they use no pesticides, only sulfur to prevent mildew, and that there really is not much noise from either sprinklers or harvesters.

Jack Davies, owner of Schramsberg Vineyards and, as president of the Napa Valley Vintners, a longtime fighter for the preservation of the agricultural aspects of the area, said flatly, "It is not practical to have agricultural and residential development coexist. It raises tax problems and requires services paid for by the agricultural interests and then the farmer can't make it over the long run.

"I have worked on these problems since I moved here in 1965," says Davies, a former vice president of Ducommun Steel. "I have a day-to-day exposure to what is going on. Some are not aware of the real pressure developing for urbanization. But the problem is real and it is unrelenting. It never goes away."

Of particular concern to Davies is a cold war that he says is being waged in a local newspaper. Davies says that last year some individual or group ran a series of ads calling for the recall or defeat of the three county supervisors who consistently vote for land-use control. In addition, since then he says a series of ads has appeared warning that land is being taken away from the people and that children's right to a home and a future are being stolen by the agricultural interests.

"These ads are so consistent and are so heavily supported, it seems to me they represent more than just a whim and I think this is only the tip of the iceberg," he said.

But valleyites are nothing if not vigilant. Even the building of a 100-unit Holiday Inn in the city of Napa was loudly protested. The complaints, according to the winemen, came because of the location, not the recently-opened motel itself. Winemen attribute the protest to the placing of the motel at the city's busiest intersection, at Highway 29, the wine road, which funnels traffic into the valley. They predicted a traffic bottleneck on an already heavily traveled road.

Little of all this subsurface tension would be noticed by the average tourist heading down Highway 29 to sample the valley's wines. At least 50 of the more than 70 wineries in the Napa Valley are open to tourists, and most of these serve free samples in tasting rooms and visitors centers. Ten years ago there were only 30 bonded wineries in all the valley.

Tourists will find the people of the valley possess a strange combination of sophistication and rural practicality that marks the wine-growing family. They are at home in the fine restaurants and the opera house of San Francisco as well as the international wine set, but their valley entertainment runs to square dancing.

Despite mushrooming new motels and restaurants in the valley, for instance, such things are practically lost on Louis Martini. "Those are for the tourists," he said. "Of course we entertain at dinner in San Francisco quite often, but most times that is business. Just to take the kids and go out to dinner here in the valley, I'll bet we haven't done that more than three times a year. Farm families eat at home."

And it is as farm familes that the winemen would like to be known. As in farm areas everywhere, sharing is a common practice in the valley. Stories abound of newcomers "borrowing expertise" from the older winemaking lands. Using a neighbor's winemaking facilities is routine among competitors in the business.

But that neighborliness does not extend to anyone who valleyites believe is threatening their area. The current fight over the resort in Calistoga, for instance, is particularly bitter.

While many of the older residents are fighting it tooth and nail, proponents see it as a controlled growth project that is a way to prevent fast-food stands and catch-as-catch-can expansion.

Putting up the money for the $20-million "Calistoga Falls" spa are architect Lawrence Simons and developer Peter Van Zandt, who was one of the principals behind three Bali resorts in Tahiti. Van Zandt insists that the spa will not hurt the basic nature of the Napa Valley but, instead, will be the rebirth of Calistoga.

"We realize the value of the Napa Valley," he said. "No one pulls up a vineyard here to plan a housing tract. We realize that the valley is a precious gift, a critical microclimate for growing grapes. tI'm not opposed to the agricultural interests. I farmed myself for six years and I'm active in the environmental fight. But no one has given a realistic alternative on how to deal with the rising growth and popularity of the Napa Valley.

"What we have here is a polarization of no-growth vs. planned growth groups. Tourists are growing at a rate of 3.5 percent compounded annually," which means the total will double in 20 years from 1.5 million annually now.

"What has been overlooked in most of the hoopla," Van Zandt said, "is the therapeutic effect of such a place. We picked Calistoga because of the therapeutic waters of the area. We have a tremendous opportunity to create an international spa with a board of directors made up of medical specialists in degenerative diseases. It would not just be a playground but an opportunity to have an enjoyable holiday plus take advantage of the health aspects of it."

But to Bernard Skoda and the Upper Napa Valley Association, it could create havoc.

"Can you imagine the traffic it would bring? With employes and everything, it would dump something like 1,000 new people on Calistoga (current population 3,350). That's a lot for such a small place. And it would bring in other business. That would mean the end of the rural little Calistoga which everyone loves, except the developers.

"I can imagine if they build this thing, in two or three years they'll be calling for a freeway to serve it. After all, people would have to come through the valley to get there. Besides, there is no water. Calistoga even rations water when there isn't a drought. How can it supply enough for a new project of this kind?"

The Van Zandt group insists there is plenty of water beneath Calistoga and that all that has to be done is to remove the heavy mineral content to make it usable. This, they contend, they can do, so the project would not interfere with the town's water supply. Under pressure of the unexpectedly heavy opposition to the project, the Calistoga City Council has held up the project until an environmental-impact study can be completed.