I'm looking for idiomatic expressions (particularly from Mexico and other parts of Latin America) to say things like "Sorry for telling you about this at/on such short notice." ... that is, how do people generally say "on short notice"?
Well the correct (and literal) translation would be:
Disculpa que te avise al respecto tan apresuradamente.
since you want to know variations more idiomatic of this kind of expression, in some places of Mexico, as where I live, would be better to say:
Disculpa que no te avisara con (más) tiempo.
On short notice (American english) or
at short notice (British English) could be simply
con tiempo or
con más tiempo in Mexico. I don't remember if there is a more idiomatic expression for this.