According to the L.A. Times ("Inauguration Is the Place for Politicians to Be Seen") and the L.A. Daily News ("Who's who list set for inauguration") here's a partial guest list for the inauguration of Los Angeles mayor and former MEChA leader Antonio Villaraigosa:

Al Gore former V.P.
Carlos de Icaza Mexican ambassador to the United States
Michael Bloomberg mayor of NYC
Fernando Ferrer candidate for mayor of NYC
Arnold Schwarzenegger CA Gov.
George Deukmejian former CA Gov.
Jerry Brown former CA Gov.
Pete Wilson former CA Gov.
Gray Davis former CA Gov.
Lazaro Cardenas Batel governor of Michoacan (MX)
Francisco Ramirez Acuna governor of Jalisco (MX)
Eugenio Elorduy Walther governor of Baja California (MX)
Carlos Rivas Zamora Mayor of San Salvador, El Salvador
"Several [other] officials from El Salvador also plan to attend... including... members of the national congress..."
Gavin Newsom San Francisco Mayor
Willie Brown former S.F. mayor
S.F. city attorney
S.F. district attorney.
Shirley Franklin mayor of Atlanta
Anthony Williams mayor of Washington, D.C.
Fabian Nunez CA Assembly Speaker
Cruz Bustamante CA Lt. Gov.
Bill Lockyer CA Atty. Gen.
Phil Angelides CA Treasurer
Don Perata CA Senate President Pro Tem
Barbara Boxer (D-Outer Space)
Rep. Nancy Pelosi (D-San Francisco)
Warren Christopher former Secretary of State
Richard Riordan former Los Angeles Mayor

There might be more.

So, why are foreign leaders attending the inauguration of a Los Angeles (CA, USA) mayor? Perhaps we should look to AV's past as well as more recent news like "AVWatch: Mexico to play important role in Villaraigosa's policies" for guidance in this matter.