if your choice would be a quick and small that being under 15 people you might choose to do a flash wedding .. some coordinating on your part you could show up at your favorite beach and just do it ..

some favs are La Jolla cove ( there is a beautiful rock formation just to the north of the tennis club)

people are there all the time taking pictures so just 1 more wedding party will blend in

just west of Hotel Del Coronado

you could contact www.elopesandeigo.com and let them for a fee set it all up

Encinitas public beach

Mission Beach at the Tourmaline street entrance

Ocean Beach (large open beach just stay away from the pier)

Pacific Beach ( drive to the the roller coaster area to park . I think my last choice,too many people)

if you want permits here is the link

http://www.sandiego.gov/park-and-recreation/general-info/permits.shtml

The other option is for the larger wedding party for that you will need to plan more .
If you are trying to go budget you could use one of San Diego beach parks .. You will need some kind of tent and a assigned help to be sure your spot of choice will be there your special day . For this kind of wedding my choice would be the Pacific beach park and the park near the Mission Beach Hilton — East Mission Bay Drive a wedding during Kite season just adds to the photo opportunities.

One drawback will be no overly loud music and no dance floor . The weather in San Diego is more than likely to be picture perfect with the proper planning, bad months would be January,February, December . The hot months by the water will be fine do to the breeze the water gives.