BALLOONING FEDERAL BUDGETS. . .; TRYING TO HOLD THE LINE

It may not have found a brass band, but President Reagan's '84 budget proposal at least met a polite reception Monday as it officially arrived on Capitol Hill.

Unlike last year's budget message, which even the GOP greeted with stony faces, the newest edition of Reaganomics has some defenders, and its opponents are tempering their criticism.

The cause of the new-found courtesy goes beyond the proposal itself. Mr. Reagan's spending plans basically continue his efforts to boost defense and shrink domestic programs. But although it is a ''stay the course'' program, Democrats and Republicans are giving the new budget consideration for three main reasons:

* Both parties see the budget as based on ''realistic'' assumptions about the growth of the United States economy.

The administration last year projected economic growth that Congress wrote off as wildly optimistic. The new budget is the reverse, proposing only a modest 3.1 percent increase in the gross national product in fiscal '84.

''The assumptions in the projections in their budget are realistic in relation to their policies,'' House Budget Committee chairman James R. Jones (D) of Oklahoma told reporters. He said that agreement on the basic economic numbers permits Congress to focus on policy issues rather than argue over economic forecasts.

Senate budget chairman Pete V. Domenici (R) of New Mexico called the Reagan budget ''cautious'' in its forecasts. ''Almost every president has submitted budgets as political documents. This is more realistic than any I know of, and it is probably on the pessimistic side,'' he said Monday.

* The White House consulted with Republicans in Congress and even appeared to make compromises before releasing the budget. GOP leaders have met with the President, and they won some concessions in the form of a $55 billion proposed cut in defense over five years. Even if many senators want more military cuts, they can see movement their way. Congressional members who have input in projects are far less likely to condemn the final product.

* Congress is still responding to the conciliatory tone set by the President in his State of the Union address Jan. 25.

''The reaction is more to the State of the Union'' than to the budget itself, says a Democratic leadership aide. "People believe that he's not expecting to get 95 percent [of what he wants]. It seemed like from the tone of the speech he was willing to go for real bipartisanship."

For all the good manners on both sides, the '84 federal budget still faces an obstacle course on Capitol Hill. And when the process is over, the budget will look very different from the one submitted this week.

It will have the easiest time in the Senate, where Republicans have the majority. But even there, members will balk at the high defense and lower domestic spending.

Senator Domenici, who praises the budget as "eminently fair." told reporters Monday that he has doubts about the Pentagon's 14 percent increasse (calculated at about 10 percent after inflation). "I'm still not convinced that we need as much as they've asked for" he said. "It's obvious that Congress will want to restrain defense more that the President or [Secretary of Defense] Cap Weinberger."

I'm very upbeat," said the Senate budget chairman as he predicted that his committee will have the spending plan ready for a vote before Easter. Last year a budget stalemate pushed the vote into summer.

Meanwhile, House budget chairman Jones is setting the same deadline for a House version, which will be a far cry from the one proposed this week by the White House.

Jones and his fellow Democratic leadership, with the help of 26 new seats and firm control of the House, will draw up a budget that will almost certainly feature a jobs program, cuts for the military, and tax proposals such as deffering the 10 percent federal income tax cut scheduled for next July.

"I believe we need an emergency program" for jobs, said House Speaker Thomas P. (Tip) O'Neill Jr. after meeting with the President to discuss the budget. During a reported "vigorous exchange," the Massachusetts Democrat urged a major jobs program to repair federal buildings and property.

Congress failed to enact a jobs program proposed by the House last year, but House Democrats are proposing to try again.

Ironically, Democrats are also planning to draw up a budget that calls for 5 to 6 percent annual growth in the GNP, much higher than the White House expects. While Democrats criticized the Republicans a year ago for making predictions that were too rosy, now they are making similar predictions. The Democrats are planning to speed up the economy by new monetary and revenue policies to keep interest rates low.

The final product on the budget will be a compromise between the Republican Senate and Democratic House versions. It will most likely be the first truly bipartisan budget since Reagan took office.