I really enjoyed driving through the Carrizo plain area. Even though, over the decades, I've driven the I-5 <-> US 101 loop between SoCal and the Bay area a zillion times, I had never taken the SR58 cut-over before. For those unfamiliar with this classic NorCal/SoCal road trip, Pacheco pass (SR 152) is the preferred cut across for the S bay, while I-580 (Tracy) serves the same function for the rest of the Bay area.
Because I've always been en route northbound or southbound, the Carrizo plain had remained a bit of a mystery. I knew it was (out) there as I passed by the turn-offs, but it's 100 miles from freeway to freeway, and the avg speed is around 35mph. In this particular case, I was driving by myself to deliver a car to my parents; I had all day, and was flying back the following day. Even though it added tiring mileage/time, it was the perfect opportunity to go for it, especially since it was spring and also because of the record rainfall.
However, if you're actually *going there* for some purpose, it's not that big of a deal mileage/time wise. From San Jose, the cut-over @ Santa Margarita is 180 miles; from OC, the cut-across @ off the I-5 is only 160 miles. Both of these drives are really easy - especially compared to getting to the Sierra - but the name of the game is leave really early. Like, say 5am. If you do that, I-5 moves @ 80mph or 2 hours. US 101 has a lower speed limit, but you can still easily get away with 70mph, or 2.5+ hours.
So, whether leaving from north or south, you can be at SR58 before 8am. It takes around 1 to 1.5 hours from there to get the Nat'l monument, which still puts you in position for a full day on day one. Just be aware that this might be (IMO) the most remote part of Calif - for instance, way more remote than Death valley. DV has the benefit of constant big-rig traffic supplying the park and surrounding communities with gas, food & supplies. SR 58 is really narrow and slow - there is no one out there, so there is neither reason to use it as a transit route or to go there to re-supply.
Which means fill up your tank at either cut-over, take a lot of water, beer, food, firewood, etc. If you do that, you should be fine. I can imagine one could satisfy their itch in just a quick 2-day, 1-night trip, especially if one is hunting for an ephemeral bloom that quickly comes and goes.
20 miles west of I-5:
There are 15mph turns on this road: