The U.S. Southwest -- after a decade that increasingly saw tumbleweeds and cactuses displaced by tract homes and shopping centers -- is having second toughts about its rapid growth.

Preliminary 1980 census figures show that Texas, New Mexico and Arizona were among the nation's fastest growing states during the past decade. What the numbers do not reflect is the increasing awareness in that popular Sun Region of the trade-offs associated with rapid growth, according to a number of analysts.

"You won't find people in Arizona standing up and cheering about our growth rate," said a pollster in Phoenix. Arizona's population grew 53 percent from 1970 to 1980, according to the Census Bureau. As a result, the ability to keep up with the demand for public services in some parts of the state " is a day-to-day concern," the pollster added.

In New Mexico, state officials would like to channel more growth in the 1980s away from major metropolian areas -- like Albuquerque, where many feel expansion has been too rapid. Growth is being encouraged in less developed areas of the state.

In Texas, "we are still optomistic about growth, but in many quarters there are questions being raised about how long this [rate of growth] can go on," said economist Victor Arnold, who is involved in long-range planning for the state. Texas' population grew by an estimated 26 percent during the past decade.

For the most part, the Southwest remains solidly in favor of growth, according to most knowledgable observers. But in all three states, officials talk of wanting more orderly population expansion this decade.

"The way we see it, growth is inevitable. The question is, what do we do with it?" said a spokesman in the Arizona governor's office. The official said water resources and public services have been strained by growth in the state's two most developed areas -- Phoenix and Tucson. The state must seek more geographic diversity in its future growth pattern and more orderly land use, he said.

Arnold is executive director of Texas 2000, a study group set up by Texas Gov. William Clements to project how long the state is likley to change during the next 20 years. The group has been in existence for only nine months, but already it offers a sobering view of what lies ahead for the nation's third most populous state, if it continues to grow at the present rate.