The romantic Old Lighthouse
First and foremost: it's a landmark situated behind the military base. Hence, entering the area is restricted by the hours of the military: from 9 to 5.
Besides, you are supposed to pay to enter the park. A 1-week pass for 1 vehicle costs 10$, however, there's another option: an annual membership for just 20$. It's a bargain and you should totally use it to your advantage.
Considering the fact that Point Loma is still in San Diego (read harsh highlights and shadows most part of the day), the most forgiving photography hours would be from 9 to 10 (especially during May-June) and from 4 to 5 (especially during winter months, where the time change gives us more promising light conditions).
The park consists of the lighthouse area (check out the spiral staircase inside of it!), some canyon looking grounds and the tidepools.
Now the parking lot might get really crowded, especially during summer months, so plan accordingly.
The tidepool area is a miraculous spot!
For starters, you can do some whale watching in the winter, watch the waves hitting the golden cliffs, breaking into millions of little sparkling droplets and take beautiful portraits with both the ocean and the cliffs.
Keep in mind that the area tends to be rocky/slippery, especialy around the tidepools area, so choose appropriate shoes and think twice before going there if you are heavily pregnant or with younger kids/pets.
The cliffs are pretty tall and abrupt, while the soil is sandy, wet, and, at times, really slippery.
And the last but not the least, don't forget that you can only park in designated areas.