Welcome to Premier.
I have done the 50CC quest a few times, usually in March around the JAX Pizza Party. I started in Santa Monica (SMO) because I lived only 15 miles from the start and it was not worth the 100 miles saving to ride to San Diego (SDO) but I have done a 100CCC starting and ending in SDO.
I advise;
Plan your route at about 80% of your expected range - know your fuel stops and have an alternative
Particularly in west Texas do not push your fuel. The combination of wind and high speed can have a surprising effect on range.
Pay attention to thunderstorms - particularly in west Texas and New Mexico.
Leaving or approaching SDO the mountain range can be cold, very cold - and the wind on corners can be dangerous. Watch also for sand in the road, particularly on corners.
I-8 is mostly wind-open but there can be enforcement. I run about 84 in AZ and CA.
Leaving the long slow-zone in Tucson, be patient. There might be a speed tax collector at the very end of the slow-zone, just before it goes back to 75mph.
New Mexico has "safety corridors" which is a code phrase for revenue enhancement zones.
El Paso has a long slow zone but usually not much of a traffic issue. I use WAZE to get through cities. If for any reason I-10 is clogged in El Paso take TX-375, Trans Mountian loop. This adds about 5 miles to your route.
Just east of ELP (near mp66) the speed limit jumps to 80mph and there is not a slow down until Kerrville. Over 450 miles, you got a rocket ship so watch the fuel.
Once you get to San Antonio, most riders I know take FM1604, Anderson Loop around the city. The fist/last couple of miles are not divided four-lane and there are a half dozen stop lights.
Approaching Houston (use WAZE) can be a crapshoot. The Sam Houston Tollway might save you time. I have a toll transponder but when I did not I blew off the tolls and did not get a ticket (I think the Wing's license plate is positioned such that the camera does not get a clear photo).
Houston to the LA state line there is a short 65mph zone and it is ENFORCED.
Once in Louisiana, the roads are going to be worse and more crowded so get used to it.
The loop (I think 210) in Lake Charles is usually no faster, I usually stay on I-10
Baton Rouge can be by-far the worst metro area as there is no loop and few alternatives. Advise WAZE but delays here can be brutal, over an hour.
Just west of Baton Rouge is a long slow zone over a swap (the whole state is pretty much a swap). Watch for enforcement.
Just east of Baton Rouge take I-12 which cuts off the drive into New Orleans, one of the great cities in the world but not for a 50CC.
You can expect a minor slow down in Mobile over a bay on an elevated section of I-10 and through a short tunnel.
In Florida, the freeway is lined with trees (just a beautiful and SUPER FLAT drive). Deer, deer, and more deer.
I-10 ends/begins at the 95 which (if west to east) you take about 10 miles to Butler Blve (FL 202) to A1A. Turn north and the GATES station is about 1/2 mile or so.
I have ridden it 13 times and love it.