San Diego since it's less than an hour away from the venue

Suggest San Diego since there is a ton to do vice staying an hour away from the city.

Weather will be in the 70s and cooler at night. No need to bring a winter jacket to sunny SD. haha

Yes

Do not stay near Hotel Circle, and I recommend not staying in Gaslamp. There are hotels downtown that are surrounding Gaslamp (Hilton, Grand Hyatt, Marriott Marquis...) that are excellent hotels. If you have questions, let me know.