i had a girl bump into me
When you say "girl," what age do you mean?
Nice people stay nice even if they're very drunk
Not all of 'em, in my experience.
Whenever I drink with people I like, they just become silly, cheerful and playful.
I think the key phrase here is "people I like" - it implies a closed circuit of friends in the environment. Out in the bars all bets are off as to the types of people you'll encounter. As JustysiaS says...
it depends on the person
I know not all polish are like this
Not all people of any nationality are like this - but some in all are likely to be. When you drink IN public, you drink WITH the public.