They wanted to call it the Hispanic Inaugural Ball, but since it was held last night they had to bill it as the first-ever official Hispanic Inaugural Reception.

"I think this is the best party in town," said Vice President-elect George Bush, as he addressed the cheering crowd in the Presidential Ballroom of the Capital Hilton Hotel. And for a lot of Hispanics who flew in from all over the country, it would be the only party in town that they were able to get tickets to during this inaugural.

Conceived only two weeks ago, the black-tie Hispanic party featured mariachi bands and folkloric dancers. The more than 2,000 guests danced the Mexican hat dance under a huge color photo of Reagan and Bush with the slogan "This Is Our Decade" written in Spanish.

"There is an unusual spirit here," said Fernando Oaxaca, chairman of the Republican National Hispanic Assembly, "because we have crossed a watershed in terms of Hispanic involvement in the two-party system."

Among the guests at the celebration were Sen. Charles Percy (R-Ill.), Sen. John Tower (R-Tex.) and Rep. Manuel Lujan (R-N.M.). Also in the throngs were son Jed Bush, who is fluent in Spanish, and his wife, Columba, who is from Mexico.

As one lapel button summed it up, the message from the Hispanics last night was "Viva! Reagan/Bush."