La Jolla weddings are usually small and almost always outdoors. Cuvier Park, the grass above the Cove, a terrace at a hotel on Prospect, or a stretch of sand at Wind and Sea. Guest counts tend to sit between twenty and eighty, because the good spots do not hold more than that and the couples who choose them are not looking for a ballroom.
The public sites require permits. Ceremonies at city parks and beaches in La Jolla are booked through San Diego Parks and Recreation, and the popular slots at Cuvier Park and Scripps Park go months ahead. A permit gives you a time window and a footprint, not the whole park, so there will be joggers and there will be photographers from another wedding waiting their turn. Confirm the current rules on chairs, arches, amplified sound and alcohol with the city before you plan around any of them.
The weather here does one specific thing. From late May into July the marine layer often sits over the coast until early afternoon, so a morning ceremony can be grey and cool while inland San Diego is bright. September and October are the clearest months and the warmest water. Wind picks up in the late afternoon at the cliff sites and it will lift a veil and swallow an unamplified voice.
Nobody plans for the sea lions. The colony below the Cove is loud, it is constant, and it does not care about your vows. It is also part of why you chose the place. Position the ceremony so the ocean is behind your guests rather than behind you if the noise concerns you, and expect it either way.