go out on the town—(coll.) go out and enjoy oneself in bars, clubs, etc.:
- We went out on the town to celebrate our wedding anniversary.
go to town—(coll.)
1. put in a lot of vigor and enthusiasm in an activity:
- They really went to town on the Christmas decorations this year.
2. severely reprimand or criticize smb.:
- When a question was asked and I could not answer he went to town on me.
Note: The expression does not correlate in meaning with the phrase go into the city—(UK) engage in commerce or finance:
- There are parents who would prefer their children to go straight from school into the city or to farming.
See also: get out of town / go to the country.