Definitely take a day trip to TJ if you have time. Night life in Mexico is pretty much strictly the 18-20 crowd.
The San Diego Zoo and Sea World are always enjoyable.
You can also check out the haunted houses. There's the Del Mar Scaregrounds near you. Also if you go downtown there's the Haunted Hotel and Frightmare on Market Street. I've heard the Whaley House in Old Town will be open for Halloween. The Whaley House is a bonafied government documented haunted house! It can be totally creepy.
I'd just like to apoligize for the crappy weather though. It's been 5-10 degrees below normal. It's been forever since we've seen 70.
Too freakin' cold!