Yes, a conductivity sensor would likely detect glycol leakage (compared to pure condensate, and provided no volatile corrosion inhibitors are used that might(?) also form conductive ions in the condensate).
1504, glycol is more of an alcohol than a hydrocarbon, not sure if the hydrocarbon detectors would work - except glycols that have been treated with fluorescent tracers (most automotive glycols have this added, it's why they look yellow/green). I'd have to look to see if pure glycols fluoresce...and a quick web search says no.