Atlanta — Already suburbanites, Betsy and Rich Brown are about to move even farther away from the city - to a 35-acre farm they are buying near the small town of Cumming, Ga. (pop. about 2,000). They don't intend to farm, but they plan to keep a couple of horses and have a garden.
The move means a 30-mile commute, instead of a seven-mile one, to their jobs at a computer firm in metropolitan Atlanta. And many shopping trips will be longer, though a new supermarket recently opened a few miles from the farm.
''Getting away from the hustle and bustle'' is the main reason for the move, says Mrs. Brown. ''And it's beautiful,'' she says of their new rural home.
They are among the most recent to jump into the stream of Americans flowing to rural places.
Since the mid-1970s, population-trend experts have been pointing out that rural America was beginning to grow faster than urban areas, reversing a historical trend. But there was considerable speculation about how long this new trend would continue. There still is.
Now, however, three of the nation's keenest observers of this rural boom say latest census data confirm that the trend continued through 1980 and is likely to continue for some time. One expert says it will last at least through the 1980s; another says it could go on for several decades.
For those joining the trend, or for those left behind (three out of four Americans still live in urban areas), the implications of rural growth are becoming clearer:
* Sprawl. The term usually is applied to urban areas, but population expert Calvin Beale, who first publicized the rural boom in the early 1970s, recounts his recent visit to some rural parts of California near the Sierras.
''Some of it just looks like San Francisco or Los Angeles transplanted,'' he says. ''Strip development'' - a hodgepodge of gas stations and fast-food restaurants - was common, especially near highway intersections.
* Higher bills. As small towns grow, more roads and sewers are needed. The debate over who should pay - newcomers, everyone in the town, the federal government - is becoming a bigger issue in many places, says Peter Morrison, population analyst with the Rand Corporation.
* Jobs. The number of jobs in the most rural of counties has been growing more rapidly than in urban areas as a whole, says Larry Long, a demographic researcher for the US Bureau of the Census. Manufacturing jobs sprang up faster in rural areas than in urban areas between 1975 and 1979, he says.
But both he and Mr. Beale, who heads population studies for the US Department of Agriculture, speculate that advantages for companies relocating in rural areas - lower taxes, an abundant supply of workers willing to work for low wages - may be diminishing. And Beale points out that federal statistics show rural unemployment is now slightly higher than urban unemployment.
All this points to the other side of the equation: urban population losses.
Eventually (no one is sure when) the ongoing loss of population from Northern metropolitan areas will end. As cities in these areas offer more retraining for workers, and have more success in attracting new industries, the outflow will finally wind down, experts say.
''My hunch is that the worst is over'' for the older manufacturing cities, says Beale.
But the urban exodus is likely to continue for another decade at least, says Mr. Morrison. It may involve a ''prolonged, agonizing adjustment,'' he says. Left behind will be the people who prefer city living and those people who cannot afford to leave, Dr. Long says.
Even some Sunbelt cities, such as Atlanta, have lost population. During the 1970s about 86 percent of the Northeast, 26 percent of the South, and 12 percent of the West's metropolitan central cities lost population, says Long.
But while Long suggests that jobs are the main rural attraction - for going there or staying there - Beale says the ''urban refugees'' he spoke with recently in rural California left the cities in search of a better ''quality of life.'' They are looking for ''peace of mind,'' a good place to raise their children, less strain, he says.
Any rural or urban place offering employment and these qualities is likely to attract and keep people, these experts say.