In the midst of the junked cars, the abandoned buildings and the clusters of men standing idle in the bright midafternoon sunshine along 27th Street in an area known here as Five Points, there is a message of hope.

"Ain't no place like this place," says the sign, daubted in red paint on the boarded-up window of an empty garage.

Unfortunately that is not the case. Despite the efforts of legions of urban planners, the number of decaying inner-city neighborhoods in the nation's newer generation of cities such as Denver, Dallas, Seattle and Phoenix is gradually growing, and urban experts are becoming concerned that these cities may be following in the depressing footsteps of their older Eastern counterparts.

Middle-class families, the traditional bulwark of the complex urban structure, are moving out. Problems such as crime and school deterioration are growing. Population in some of the newer cities has stopped growing or has begun to decline after a spurt in the last decade or so.

"The same process that took place in Baltimore or Philadelphia is taking place now in the newer cities," said Sybil Phillips, specialist in neighborhood patterns for the U. S. Department of Housing and Urban Development. "We're beginning to become very definitely concerned about these cities."

Heavey growth in recent years, particularly in and around the Sun Belt cities of the South and Southwest, has masked some of the problems, according to urban experts "To the casual eye of the outsider not much blight is evident," said Alan Sieggel, another HUD urban expert.

"But," Siegel added, "there are vacant buildings, deteriorating neighborhoods and holes where urban renewal has torn things out and nothing has come in to replace them but parking lots."

Perhaps nowhere is the split urban personality more evident than there in Denver.

With the development of oil, gas, coal and uranium resources in the Rocky Mountain states Denver has become a hub of energy growth, and many energy-related firms are opening branch offices or shifting their operations here. The city's downtown is awash in new construction and office space is at a premium.

Last week, however, Denver's Office of Policy Analysis released a report showing that nearly half of the rental residencies in the inner-city area here are either substandard or marginal. Noting the inner-city problems of New York and Newark, the report warns "the experience of these older Eastern Seaboard cities is a grim indication of what the future could hold for newer cities like Denver."

Nor is Denver along in the drift toward urban light. Dallas, at the heart of the Sun Belt, is also wrestling with problems of inner-city deterioration. Dallas officials have created several "historic districts" in rundown areas to try to control inner-city deterioration.

"It has been recognized that if Dallas doesn't do something to cause a turnaround our center city could end up the same as those of the Eastern cities," said David Ryburn, a Dallas city planner.

Last spring Seattle released a report noting an inner-city housing decline there. Phoenix, which has already lost some of its commercial development and office construction to the suburbs, is now in the midst of a three-year study to try to reverse the trend. A committee of about 100 Phoenix civic leaders is investigating the possibility of a new type of urban design based on the development of up to a dozen urban "villages" scattered within the city's borders.

The idea, said Phoenix planning department director John W. Beatty, is to use the concept to arrest the spread of urban blight. "We're trying to catch it now while we can before history repeats itself here," Beatty said.

Denver, which is neither a member of the youngest set of cities like Phoenix nor one of the older East Coast urban generation, is at a critical point in its development, according to urban planning experts here.

Under a 1973 amendment to the state constitution the city is prohibited from annexing suburbs, and population has started to decline slowly, from a peak of about 515,000 in 1970.

Neighborhoods like Five Points have begun to push outward as the city's core business area has expanded. Ahead of this circle of blight, many of the city's middle-class families, helped alaong by their unusually strong ties here to the automobile, have headed for the suburbs. The process, planners here note, is a repeat of the "white flight" pattern of many older Eastern cities.

In Five Points, once a fairly healthy, racially mixed area of bustling all-night barbecue stands and small shops, most of the residents are black and many are jobless. In addition to a high rate of street crime and unemployment the area has suffered from what planning experts here call "institutional disinvestment."

According to the analysts, mortgage lenders have shied away from redevelopment efforts in areas like Five Points. At least 40 per cent of the landlords - most of them absentee owners - indicated they are planning to pull out withina year if they can find buyers for their properites.

"Nobody really knows how these things will go in the future," said Kyle Davis, a Denver planning specialist. "But we're operating on the idea that it will follow the same pattern as in the older cities."

If anything, Davis and other urban analysts say, Denver's situation contains the possibility of even more rapid deterioration. Like many of the newer cities, Denver has tended to restruct the use of public capital more than older cities. Boston and Philadelphia, for example, used public funds to stimulate private downtown rehabilitation efforts, but Denver's charter prohibits this type of funding, Davis said.

Nor have federal aid programs proved particularly effective here. Because of a quick in HUD's regulations defining "fair market" rents, Davis said, returns on rehabilitation projects are too low to attract either the fulltime landlord, who would be likely to live in or near his project, or the big developer looking for a tax shelter.

The result is a continued movement toward the suburbs, experts like Davis say. Crime and urban deterioration push the middle-class population farther away from downtown until eventually businesses begin to break off from the inner cities and follow their work force to the suburbs.

The pattern is still in a relatively early stage here and Denver, like Seattle, Dallas and other younger cities, has tried to reverse the flow by attempting to lure affluent singles and childless couples back to inner-city areas.

A controversial report last spring by Seattle planners actually urged the city to concentrate on this population segment and, in effect, to write off the possibility of regaining many of the white, middle-class families who have left for the suburbs. The report suggested that city development be aimed at apartment construction and office buildings instead of commercial structures and family type dwellings.

Dener has not yet taken a similar stance but Davis and other planners here noted that the trend is flowing in the same direction. Most of the city's new construction has been in smaller apartments and shopping and entertainment complexes geared toward affluent, younger singles. School enrollment dropped by nearly 10,000 to about 60,000 students in the last five years.

"We don't see this as an unchangeable flow and we haven't given up on attracting families," said Davis. "But we have to face facts about what's happening to places like Denver and the facts are that these are the people who have the money and who can help us most to hold on to what we've got."