Can I drink alcohol with diverticulitis.?

Yes. Although some antibiotics treatment may interfere with your alcohol so check with your doc.
Best not to. You should avoid alcohol with diverticulitis because it suppresses the immune system, thins the blood which can worsen bleeding, and may interfere with some antibiotics. If you mean diverticulosis, which is having the colon pockets without pain or infection, then moderate consumption of alcohol is fine (2 drinks daily for men, 1 drink daily for women).