If you do choose to have a cash bar, you should let your guests know ahead of time, probably on their invitation. Most people these days expect some sort of open bar, and many women dont even bring a wallet, never mind actual cash.
Furthermore, who pays for open bar at wedding? Tradition. Typically, whoever is paying for the wedding and reception will pay for the open bar, should the couple choose to have one. Traditionally, this responsibility falls on the brides family.
Consequently, what does open bar mean on an invitation?
“Open Bar” means that your drinks are included in the cost of your admission to the party. You can order your favorite drink and bask in the awesome taste and the relief that you are not to be burdened with a bill! The best parties usually offer “Open Bar” services.
How do you tell guests they have to pay for drinks?
If the bar will just be open and you are expecting people to pay for their own drinks, I would word it as cash bar. That pretty much means that you pay for your own drinks. If you mean that you are paying for the drinks but not the food, I would put something like appetizers, etc available for ordering.