Ok, bartender/EMT authority here. Yes, alcohol tends to make people honest. It also tends to make them do and say incredibly stupid things. Telling which is which is not based as much on the person as what they're talking about. If you ask someone their opinion on something when they're drunk, they'll probably give you an extremely honest answer. There's a but, however. That answer may only be true WHILE they're drunk, if it's about whether something should be done. Seeing as their judgement is busy drowning in ethanol somewhere in their liver, they may have one opinion when they're drunk and a completely different one when they're sober. If they're just talking about random crap, most of the time it's just general stupidity. Hell, I once spent a drunken evening convincing an entire bar I was Scottish. Just think logically about what things would be altered by being drunk, usually you can tell with just common sense.