SAN ANTONIO (AP) _ Police in this Texas city have guarded popes and queens, but protecting President Bush and a half-dozen other foreign leaders at one time is duty of a different dimension.

The leaders of Mexico, Bolivia, Colombia, Peru and Ecuador and the foreign minister of Venezuela were joining Bush here for a two-day Latin American summit on combatting the plague of drugs.

At the last drug summit two years ago in Cartagena, Colombia, security was of paramount concern as there had been highly publicized death threats against participants. There has been less talk of that this time, but concern about protecting the leaders is still high.

Since 1987, Pope John Paul II, Prince Charles, Queen Elizabeth II and Mexican President Carlos Salinas de Gortari have been among the international dignitaries to visit the city.

''The other visits by VIPs were advantageous,'' said police spokesman Sgt. Paul Buske. ''It resulted in creating a group of experienced command officers to handle VIP visitations,'' he said.

This time, they'll have to watch five hotels where the seven delegations will be housed.

Summit planners chose the McNay Art Museum for the San Antonio drug meeting in part because of its enclosed ''campus atmosphere,'' said White House summit director Ed Cowling. The Spanish-style mansion is on 23 acres of fenced-in land that officials say can be well secured.

The White House rejected a downtown river parade proposed by the city, partly for security reasons. Few details on schedules or motorcade routes have been released to the public, and citizens hoping to spot the presidents in public may be out of luck.

No speeches or other public appearances are planned.

Police Wednesday arrested one former police officer who was armed with a loaded pistol and posing as head of Mexican security.

Sheriff Harlon Copeland said the detained man, Victor Manuel Tapia, apparently meant no harm. ''He just wants to be a big shot,'' Copeland said.

---

People gathering in San Antonio to protest the government's drug policy range from proponents for legal marijuana to AIDS groups advocating needle exchange programs.

''This time we're going to see tie-dyes along with suits and ties,'' said John Gibbs, organizer of an ''alternative summit'' that will take place while the leaders are here.

Some of the opposition groups want all drugs legalized. Others want President Bush to shift his emphasis from enforcement to prevention and treatment.

Joey Tranchina, California director of the National AIDS Brigade needle exchange program, said he will urge support for clean needle exchanges to help stop the spread of HIV, the virus which causes AIDS.

The majority of AIDS cases among women and babies can be traced to dirty needles, Tranchina said.

---

The jet carrying the Venezuelan foreign minister to the summit experienced an in-flight emergency, causing anxious moments before the plane landed at Kelly Air Force Base, the crew said.

About 20 minutes before landing Tuesday night, the Falcon 50 aircraft carrying Foreign Minister Armando Duran and his delegation experienced an electrical problem on its flight panel. An instrument shorted, causing smoke in the cockpit, base spokeswoman Maj. Donna Pastor said.