What can I do this coming Tuesday in downtown San Francisco?

I’m flying-in to San Francisco Monday afternoon, and staying at the hotels by the Moscone Convention Center. I have Monday evening and all of Tuesday to myself before the convention gets going for me on Wednesday. Can you please recommend:

- a good (but not dressy!) italian restaurant for lunch and/or dinner that’s walkable from the convention center area

- something to do on Tuesday that’s walkable from the convention center area

Thank you, San Franciscan jellyfish! :)