With a mild diverticulitis attack must you take antibiotics or will a liguid diet help?

It would depend upon the symptoms that you have been observing with the mild attack of diverticulitis, some of the symptoms are; the most common symptom of diverticulitis is abdominal pain. The most common sign is tenderness around the left side of the lower abdomen. If infection is the cause, then nausea, vomiting, feeling hot while having no fever, cramping, and constipation may occur as well. The severity of symptoms depends on the extent of the infection and complications. Diverticulitis worsens throughout the day, as it starts as small pains and slowly turns into vomiting and sharp pains.

Treatment
An initial episode of acute diverticulitis is usually treated with bowel rest (i.e., nothing by mouth), IV fluid resuscitation, and broad-spectrum antibiotics which cover anaerobic bacteria and gram-negative rods. However, recurring acute attacks or complications, such as peritonitis, abscess, or fistula may require surgery, either immediately or on an elective basis.

Most cases of simple, uncomplicated diverticulitis respond to conservative therapy with bowel rest and antibiotics

You must seek medical advice, drinking a lot of fluids shall be good, but do not self medicate, be well & safe!