If dining out risks being an embarrassment to you or the person you're caring for -- because your companion has trouble choosing what to order or sometimes says inappropriate things -- you needn't give up this kind of outing.
Instead, consider using a discreet card of explanation. Write on a small business-sized card, "My friend (or parent or spouse) has a memory problem. Please address your questions to me." Discreetly hand it to the hostess (or server) when you're seated. The point isn't for your companion to be ignored but to avoid having him or her feel put on the spot. And you won't have to make potentially awkward explanations.