I always like to get out and ride in areas I visit, especially beautiful spots like SD.
I recommend renting a bike, take ferry to
Coronado Island (close to hotel) and riding the Silver Strand. https://en.wikipedia.org/wiki/Silver_Strand_(San_Diego)
Nice 7+ miles you can ride at speed to Imperial Beach area and then return.
Do a few intervals, I found it pretty fun and look forward to riding it again.
For hill training, you really want a car to drive up the coast,
Mt. Soledad would be fun.
A few other challenges ...San Diego's Toughest Road Climbs
https://smorgcycle.blogspot.com/2014...bs-little.html