President Reagan said tonight that he believes the House and Senate will reconcile differences on the budget with "little trouble" to give him about three-fourths of the spending and tax cuts he was seeking.

Speaking to a $1,000-per-plate fund-raiser for Texas Gov. Bill Clements, Reagan said approval of a budget resolution would send money markets the signal they need to bring down interest rates but he avoided making his usual forecast for the beginning of economic recovery. He also predicted that it would cause a substantial decrease in the budget deficit.

Tonight's fund-raiser, which attracted an assortment of former Democratic officeholders in Texas who have endorsed the Republican governor's bid for a second term against Lt. Gov. Mark White, was expected to raise about $3.5 million. Reagan called it a "political dinner . . . but not a partisan dinner."

Among the Texas Democrats were former governors Preston Smith, Allan Shivers and Price Daniel, plus John Connally who was a Democrat before switching to the Republican Party. Reagan praised the Democratic members of Congress who supported his economic program.

Former president Ford also addressed the dinner. Once a bitter rival, he strongly praised Reagan for the steps he has taken to turn the economy around. "Mr. President, we're on the right road and I can assure you, Mr. President, that this sharpshooting by many, many Democrats will not be swallowed by the American people."

A few hundred demonstrators protested outside the downtown convention center, booing the oilmen, real estate developers, bankers and others as they entered.

In his speech, Reagan rehashed familiar themes, taking credit for the sharp decline in the inflation rate while lamenting the recession and the rise in unemployment, which he blamed on Jimmy Carter.

"Please do not think I am trying to minimize the tragedy of unemployment, which plagues us and which has been steadily increasing since 1979," he said. "As one who entered the job market in the depths of the Depression in 1932, I bleed for the man or woman able and willing to work who finds no job opening."

In returning to his discussion of the economy in his first major speech after his 10-day European trip, Reagan spoke with an uncharacteristic defensive edge about his critics. He said he expected there would be "loud voices" contending--unfairly, he said--that the spending cuts for the elderly, poor and handicapped were too deep and the defense program was out of proportion.

Houston Democrats staged a counter-dinner at the same time at a nearby hotel. They charged $5 a head and drew more than 3,000 people.