The best thing to do in this situation is to ask someone involved in the wedding planning, if you can bring a guest to the wedding. It is not recommended to just show up with a date in tow.
I’m sure you have heard before how expensive weddings can be. The bride and groom have spent many hours trying to budget, plan and ensure that everybody close to them have an opportunity to share in their nuptials. Having an extra person to budget for, might not be an option for them, so don’t take it the wrong way if they say ‘no’