If you're looking for club head speed, GCQuad gives you the most accurate reading. Trackman 4 is great with ball data but not perfect with club head data.
There is also a difference in reading from Flightscope and Trackman data. Flightscope measures club head data right at first impact (when the club contacts the ball) whereas Trackman measures club head data at full compression which means Trackman will show lower club head speed vs Flightscope.
I'm in SoCal too and I love doppler radar tech, but none of these bays are outdoors and doppler radar tech definitely takes a backseat to GCQuad indoors.
Roger Dunn in West LA has GCQuad and allow you to rent out one of the private bays. One of the workers will be with you since they're technically supposed to be doing a fitting, but they're cool about you just wanting to get baseline data. It's $150 for an hour though.