Wow, this is kinda interesting for me... I've lived in the Midwestern United States all my life (21 years) and I hear 'hiya' used all the time. It's weird that nobody else has...
In any case, it's a pretty informal greeting typically used between friends or in very casual situations. You may not want to use it in business settings or formal situations. Or when you're just meeting somebody for the first time.
It's not odd if a non-native speaker says it, as long as it's in the correct context.