Mornings on the 5 the northbound out of San Diego is mild as is Southbound out of Los Angeles. Reverse that in the Evenings. The only major problem with that route is that it is the only north south artery except for route 15 on the other side of the mountains and long way around.
For example, mom and me were going south on the 5 just north of Oceanside and something happened involving a bad person. The whole freeway got shut down and we came in on the tail end of the tie up and it took a lot longer.
I would not worry about making the trip unless at border check you act like Dale Dribble from King of the Hill show.
Just make sure you are wide eyed and wide awake there as sometimes you get some really dangerous people as in merging while leaving you a foot to spare or slowing way down or worst is when you are driving behind someone and at the last minute they stop. Oh we have to stop on the freeway, DOH.
I love the trip and keep your eyes open for hawks and seabirds. It is not Story, Indiana or the Redwoods but a very nice drive including farmland, a nuclear power plant, and near
Legoland a nice music museum. Down that way is some nice flower farms also.
Also use google maps to see the view where you see images of the street so you can get used to the 405 split and the 55 split and the 57 split. It is pretty straightforward and just stay in the lanes marked for the 5 freeway but watch for people who at the last minute DOH lane change.
In n Out has the best burgers and for a mess order animal style or with grilled onions to for the he-man a 8X8 which is 8 slices of cheese and 8 slices of meat, oy.
