The reaction at both ends of Pennsylvania Avenue yesterday to the fiscal 1984 budget President Reagan is sending Congress is that he generally has stuck to his principles, but not so hard as to preclude a possible compromise on the shape of future taxes and federal spending.

Reagan told reporters he would be "just as stubborn as I ever was" in demanding cuts in some previously "untouchable" domestic programs, but conceded, "You don't ever get 100 percent of what you ask for."

Key legislators of both parties talked about a "donnybrook" on defense and domestic programs, but the consensus supported the prediction of House Minority Leader Robert H. Michel (R-Ill.) that Reagan's proposal will "not simply be discarded out of hand," as happened last year in Congress.

Reagan made significant changes when confronted with the prospect of huge budget deficits for many years.

House Budget Committee Chairman James R. Jones (D-Okla.) said the White House had made it clear "this is going to be a give-and-take year and not a take-it-or-leave-it year."

Although Senate Majority Leader Howard H. Baker Jr. (R-Tenn.) said the proposed freeze on many domestic programs would be "a bitter pill" for many people, the initial reaction among congressional Democrats was that Reagan's version of the freeze was less drastic than they had expected.

Still, major battles loom over proposed changes in Social Security, Medicare and the Civil Service retirement system, as well as over Reagan's determination to resist any major cutbacks in the defense buildup.

Even before yesterday's briefings of Republican legislators led to a flood of leaks on the budget, which will be sent to Congress formally on Monday, many lawmakers of both parties had expressed skepticism about the practicality of Reagan's contingency plans for tax hikes starting three years from now.

Michel said the president would end up fighting a defensive tax battle to save the indexing of tax rates that is scheduled to take effect next year.

And yet another fight looms over a public works jobs program, with Baker predicting that there will be "a jobs bill of some sort."

House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) spoke of a $5 billion to $7 billion price tag, which White House spokesman Larry Speakes said Reagan would surely reject.

For all the static, there was agreement on both sides of the aisle that Reagan's budget proposal for the 1984 fiscal year is not likely to suffer the outright rejection it did in 1982, when the Senate Budget Committee unanimously set it aside and the House never brought it to a vote in anything resembling its original form.

The budget Reagan is sending Congress Monday envisages saving almost a quarter of a trillion dollars--$244 billion--in the next five fiscal years in such programs in an effort to trim the ballooning budget deficits.

By contrast, federal grants in aid to states and cities and spending on most "discretionary" domestic programs will be held at about the same level as the current year, and a few programs--Head Start for youngsters, science grants, the anti-drug drive--are scheduled for increases.

Partly for that reason, many of the members of Congress who were briefed yesterday expressed relief at the budget figures they had seen.

The uproar may increase when copies of the full budget circulate on Capitol Hill Monday. Even yesterday, there were signs of trouble ahead for some of the contingency tax increases that Reagan will be asking to reduce budget deficits later in the decade.

The president defended those tax proposals in a brief interview with reporters who had gone to the White House for a background briefing on budget and foreign policy issues with other senior administration officials.

While Baker and Senate Finance Committee Chairman Robert J. Dole (R-Kan.), among others, have criticized the request for a stand-by income tax surcharge and energy taxes starting in fiscal 1986, Reagan said he thought there was "considerable agreement" from Republican leaders generally "on what it is that we're proposing."

The plan calls for raising almost $50 billion a year for three years from a 5 percent surtax on individual and corporate tax payments and a $5-a-barrel oil excise tax, starting in fiscal 1986.

A reporter asked Reagan if that proposal--along with last year's $98 billion tax increase and the payroll tax speedup that is part of the Social Security rescue package the president has endorsed--was not evidence to conservatives that "the Washington buddy system is . . . wearing you down and that a lot of the things you were elected to . . . just seem to be fading away."

Not so, Reagan said, blaming the impression on "a lack of complete information." While conceding that "you don't get 100 percent each time . . . particularly when your party is not in control" of both houses of Congress, he said he had "turned the whole debate around."

"For years and years, the minority, the Republicans in Congress, have been fighting a rear guard action against the ever-increasing proliferation of government programs . . . that were supposed to make paradise out of this earthly sphere. And today, the debate is focused on how much or how little will the cuts be in government spending."

Reagan insisted that, despite the tax increases he has endorsed, the effect of the three-stage income tax reduction he pushed through Congress in 1981 will be to leave an additional $750 billion in people's pockets.

And he noted that the standby tax boosts he is requesting for later in the decade would go into effect only if Congress accepted the spending cuts he has asked for and the deficit still remained higher than 2.5 percent of the gross national product, while the economy continued to grow.

"If it were just out there as a contingency proposal with no restrictions," Reagan said, "I could see the spenders up on the Hill then going right ahead and saying, 'Why cut? We'll just wait and have that tax increase.' But they can't do that . . . and I think many up on the Hill see that."

On the other hand, the president, who came to office determined to shrink taxes and federal spending, conceded it was impossible to balance the budget at the levels of taxes left by the 1981 tax measure.

Pointing out that that three-year tax cut had reduced revenues to less than 19 percent of gross national product--well below his original target of 20.6 percent--Reagan said, "there is no way that you can cut spending enough to bring spending down to 18.5 percent. And so we were willing to do what we did."