If you are on FF from the start...I have yet to ever be denied LAX clearance on one of the transition routes in over a dozen trips over the past few months...even on stupid busy days where I though the controller was gonna snap and loose it. Always have a plan B...but LAX transitions are pretty easy once you learn them. I am always a fan of the coastal route, always seems to be quiet but there are plenty of other depending on your altitude.
You can pretty much hug the shore and still have plenty of glide distance, even at 5500'...especially if you have Foreflight or a good GPS to keep you clear of the Restricted space.
If you look and plan carefully, you can get to KMYF without entering SAN Bravo from the Northwest. They do literally hand out Bravo clearances like candy without even requesting. If you are above 3200' and below 6800'...you can make it all the way and remain clear if needed.
Key to So Cal flying in my opinion is all about FF from the start and they will get you where you need to go, They would rather have you in the system then have to dodge their IFR traffic around a random 1200 target with no contact. If you show up and knock on their doorstep at the last second, that is where I have heard other pilots having problems with clearances.