"on vacation" = "on a trip" I'm going ON A TRIP to Hawaii. I'm going ON VACATION to Hawaii. WHERE are you going + FOR WHAT PURPOSE you're going somewhere Where are you going for your haircut? for your prom dress? for vacation?

Using "on" is all right, but "for" is slightly better because "for" indicates "over a period of time".

We do say 'go on holiday. We don't say 'go for holiday' usually but you will hear 'go for a holiday'

California, City=San Diego to see family and go to sea world then a few months later to tampa, florida for the beach action and disney world

Where are you going on vacation? = correct Where are you going for vacation? = correct, 更口语的