If you're only going out for a few drinks (i.e. 2~3) then there shouldn't be too much a problem - just be really aware of how you're feeling and have something carby afterwards as the alcohol will make your blood glucose lower several hours after you've first drunk it. I did this anyway before diabetes as the carbs stopped me getting too drunk and reduced the hangover the next day - pizza/pasta is always a good bet. Or alternatively you could just have a sweet drink as in my personal experience stuff like cocktails or vodka and regular coke (vodka has no carbs) tends to "balance out" my BG levels. This is a good idea especially if you plan on going out to a club or somewhere where you'll be dancing through the night.
If you're going out to a pub or restaurant then testing regularly shouldn't be a problem (as opposed to a club), so that's always a safe option if you're unsure. Also, tell your friends about your diabetes (if you haven't already) so they know what to do if something does go wrong.