There are lot of free chargers in San Diego. Just download the Volta app and drive to one near you. There are some free DC Fast chargers too but they are less common and not obvious. I discovered one last weekend that charged my Kona at a 59kwh rate, and when I got the final receipt it was for Zero dollars, nice that. For me so far, I've been charging my Kona about 90% of the time for free. I'm fortunate enough to be adding solar panels today and thus will likely stop using the free chargers in the future.
Oh, and Tier 1 rate for electricity in San Diego averages $.21 a kwh. Between 4pm and 9pm it doubles. Tier 2 and 3 rates are even higher. You can however pay a $16 a month fee to go on a plan that allows you to get electricity at $.09 a kwh between midnight and 5 am.