I have not gone directly from Marina Del Rey to Santa Cruz but I have sailed that area. You need to give Point Dume a wide berth. The winds blow a lot harder around that area and the seas get rough. If you cut it close, as on a direct route, you will have the wind and the current on your nose. The seas build to a high short chop. It is not a comfortable place to be.
Agree with the wide berth around Dume. You're looking at a full day of sail/motorsail to get to Ventura Channel Island Harbor. If you go there from MDR, night sailing is unavoidable. Ventura to Channel Island should be cake (in comparison) the next day.
There is also Santa Barbara Island. the back side is pleasant but wide open to the South swell if there is one. I might do a straight shot up to Channel Island Harbor then make my left to Santa Cruz. There are plenty of anchorages when you get over there. As always watch the weather and the whales both are hit and miss.
From MDR to Channel Islands harbor is about 48 miles. It should take you about 10 hours. The are guest docks in the harbor to stop at. The trip to Santa Cruz (Chinese Harbor) from Channel islands is about 28 milse direct. To sail there, with the normal winds will be about 33 miles. The sail there can be quite nice. I would not stop at Paradise cove and then head to Santa Cruz. It is 19 miles from MDR to Paradise cove, And then 55 miles to Santa Cruz.
Leave early in the morning (as in O-dark-thirty) and try to keep your speed above 5 kts by motor-sailing when you have to. Head due west (true) until you get just past Pt. Dume (keep at least two or three miles south of Pt. Dume) then WNW, staying just to the east of the shipping lanes, until you get close to the Platform Gail. From Gail head SW to Scorpion Anchorage (going from Gail to Scorpion will keep you more or less perpendicular to the shipping lanes as you cross, limiting your time dodging the big boys). All together, it's about 60 nm, so expect something close to a 12 hour sail. Use the area between Platform Gina and Platform Gail as a sort of decision point. If when you get in that area you can't realistically expect to get to Scorpion before sunset (sunset, not dark), turn toward Channel Islands Harbor and spend the night there. If you get to that decision point and find that you can realistically make it to Prisoners Harbor before sunset (not likely in a boat that size, except in the summer) divert to Prisoners, as it's usually a better anchorage anyway. But, always be prepared (and willing) to high-tail it to Channel Islands Harbor, or Ventura, or back to MDR if that seems to be more prudent.