Now a days, if you are lucky enough to find a donkey show anywhere in Mexico, it will be a beer drinking burro, maybe a tequila drinking ass.
According to my dad (born in TJ in 1936) the last donkey show in TJ took place sometime in the mid 1950's; it was killed because of political reasons (it gave TJ a bad image) hasn't been revived since.
For the record, there hasn't been a donkey show in TJ in the last 50 years, anyone under the age of 70 claiming to have seen a donkey show in TJ is bullshitting you.