CA Coastal rentals are high $. AND, it does depend on what you want.
You can get a 1 bedroom unit at the San Clemente Inn that sleeps 6 during that time for $900, but it's 2.5 star accommodations.
You could get a Marriott in Newport Beach or an Aviara in Carlsbad for about $3K.
You could get a 1 bedroom unit at a place like the Carlsbad Inn, Carlsbad Seapointe or the Southern Cal Beach Club, and do what many do-- cram in 6. You can get this for about $1400, and the accommodations would be 4-5 star.
Proximity to the beach also has an impact on rental costs.