Ronald Reagan's bandwagon lost its momentum when it came to tax-reform measures on state ballots yesterday, most of which lost despite backing from Reagan supporters. An unprecedented 43 states listed referendum issues that included efforts either to boost or to crack down on nuclear power, gambling, drinking, smoking, cohabitation and the Spanish language.

In spite of recent political and racial trouble, Miamians passed a controversial ordinance that will prevent Spanish from being used in public signs, emergency 911 calls, hurricane warnings and other public statements. The vote was running 7 to 4 to curb the use of Spanish.

Most Hispanics regard the proposal as a slap in the face, especially since Spanish has been established officially as the area's second language since 1973. "It will be the most destructive thing that has happened to this community," said Eduardo Padron, chairman of the Spanish American League Against Discrimination.

The ordinance will prohibit spending any Dade County (Miami) funds for use of any language other than English, or for promotion of "any culture other than that of the United States." That last phrase has drawn special fire not only from Hispanics but from blacks as well, who question what "United States culture" is.

Emmy Shafer, an immigrant from the Soviet Union, led the drive for the 26,000 signatures necessary to get the issue on the ballot. "How come the Cubans get everything?" she asked. She immigrated to the United States after World War II and said she wants to return Miami to the "way it used to be."

The ordinance will not cut out all officially sanctioned Spanish language use, because the federal and state governments have supported such programs as bilingual education in the schools, and the use of Spanish interpreters in hospital emergency rooms. The full effect of the ordinance, both socially and linguistically, is still uncertain.

Clones or shadows of California's successful Proposition 13 of 1978 all went down to defeat in Arizona, Nevada, Utah, South Dakota and Oregon. In Michigan, three tax initiatives appeared to have failed, winning less than 45 percent of the vote. Sentiment in the state had been slowly turning against the most controversial of the three, one that would return property-tax valuations to 1978 levels and then cut the tax itself in half.

Gov. William Milliken led the opposition, arguing that it would cut the state's general budget by 60 percent, enough to kill the state university system, close state mental hospitals and require the layoff of three-fourths of the state police and a third of all state employes.

Montana was voting by almost a 2-to-1 ratio in early balloting to change state tax law so that levies could not be increased just to keep pace with inflation, while other tax-cut proposals appeared to have won in Missouri and Arkansas.

In Massachusetts, where residents pay the nation's second-highest property levies and call their state "Taxachusetts," a major tax slash appeared victorious by 3 to 2. Proposition 2 1/2, as it is called there, would set a 2.5 percent limit on property-tax valuations, a cut from the current 3.4 percent average.

In Ohio, a "Fair Tax Initiative" backed by a liberal coalition was losing 5 to 1 in early returns. It would have granted middle-class homeowners new tax credits while increasing taxes on the wealthy and large businesses. Gov. James Rhodes had claimed it would make the state "an industrial wasteland," but the Ohio Manufactures' Association failed in 16 lawsuits to keep it off the ballot.

District of Columbia voters were approving a try for statehood by a 5-to-4 ratio, while a legalized gambling proposal was winning 2 to 1. Gambling initiatives were also up in Colorado, Arizona, Texas, West Virginia and Missouri.

Antinuclear measures were on the ballot in six states, and the results were split.

In a major victory for antinuclear forces, Washington state voters apparently have decided by 2 to 1 to prohibit nuclear waste from being brought into the state. This step would effectively shut down the large Hanford waste disposal site, one of only three facilities for low-level wastes in the United States.

Another antinuclear victory appeared possible in South Dakota, where the referendum would require voters to approve any future nuclear plant, waste disposal site, or uranium mine. The measure was passing 51 to 49 percent with about a quarter of the returns in.

In Oregon a similar measure was getting a 50-50 vote in early returns. The proposal would require voter approval of future nuclear plants, and also require the nuclear plants to find a safe site to dump radioactive waste before being licensed.

The only one of the six measures that would have halted ongoing construction of a nuclear plant was in Missouri and failed there by almost a 3-to-1 ratio. It would have required nuclear plants to have a federally licensed site for the disposal of radioactive waste before they would be allowed to operate.

Another restrictive measure, this one in Montana, would have halted the milling of radioactive wastes in the state. The measure failed by 5 to 4.

The sixth nuclear test was in Massachusetts, where the voting was by counties and was nonbinding. The results were scattered and confusing in early returns, with both sides claiming victory.

A move to add the Equal Rights Amendment to the Iowa state constitution appeared to be failing by a 3-to-2 ratio.

In Nevada, four southeastern counties were venting their feelings about the expected coming of the MX missile. Utah voters decided that women should not be allowed to work in underground mines, Oregon residents that fur trapping should not be banned, and South Dakotans that the hunting of mourning doves should be permitted. Opponents had argued that the bird is a treasured peace symbol, but the victorious proponents preferred to see it as a good dinner.

Washington state defeated an unprecedented proposal that would have begun the transfer to the state of 314,000 acres of federally owned land. It was the first popular test of strength for the so-called "Sagebrush Republican" of western states that are annoyed at remote control from Washington of much of their territory.

Recognizing that couples in our time often live together for some time before marriage, Alabama had a constitutional amendment on the ballot that would terminate alimony to a person who either remarries or "lives openly with a member of the opposite sex."

In New Jersey, four of six counties rumbling lately about becoming an independent State of south Jersey had approved a nonbinding expression of sentiment in that direction. Two others vetoed it.

Voters got a chance to ban smoking in public places in two areas of the country, one in Miami and the other in California.

Among the more unusual ballot items was a vaguely worded amendment to Florida's constitution that would attempt to protect citizens to some degree against technological advances and state intrusions through technological devices. The amendment declared that bureaucracies should not interfere with a citizen's "right to be left alone." It was passing 3 to 2 in early returns. a