Welcome!
As for allowed areas, your first step should be to check Airmap or Kittyhawk and see whether LAANC is needed/available in the areas you want to fly.
As for those specific locations, here is what I've found:
1. Shoreline Park: Most of the airspace around Shoreline Park in Mountain View is controlled airspace on account of Moffett Airfield. This airfield unfortunately doesn't support LAANC last I checked. I think there were also signs posted around here (last I checked) saying "no drones" so it's probably best to respect those wishes as well.
2. Rancho San Antonio: You're not allowed to operate a drone in the park. See the regulations here:
Rancho San Antonio Preserve | Midpeninsula Regional Open Space District
3. Vasona Park: This is a county park, so as per SCC regulations you'd need a permit to operate a drone here:
The 5 Best Places to Fly a Drone in San Jose (2021) | UAV Coach
Unfortunately many of the areas that would seem nice to fly in are restricted like this in one way or another. However that doesn't mean there's no place to fly and practice!
Near Sunnyvale, I usually flew around Twin Creeks Park - lots of open space and not many people if no games going on. LAANC is available in the area around there. The area around Crossman/Java/Moffett Park Dr is also OK to practice since last I checked it was mostly empty company buildings around there and parking lots and hardly anyone around. Again LAANC is required.
I also fly around Pacifica and Half Moon Bay. Berkeley Marina is also a nice place. (The weather was great today and I actually just got back from flying near Rockaway Beach in Pacifica)
@pelagic_one probably has some nice recommendations for the Bay Area.