I know Spacex is building a starhopper (starship prototype) in Texas and Florida. Could they also build a starhopper prototype at the Vandenburg, CA launch complex? I know Vandenburg is better for polar orbit (launch towards south) but is that the only reason? Did the Air Force or some other law or policy in CA restrict this type of testing?
SpaceX did originally plan to build the BFR in the Port of LA but they pulled out, here is an article about that. They also looked at other states to place their test site for their hops and after negotiating with the local and state governments and then the FAA. Brownsville was selected. A lot of those talks aren't public other than public hearings and FAA environmental studies. Texas was also very supportive to SpaceX's plan to build a Spaceport there and I believe those plans are still in motion. There's probably nothing physically stopping them from testing at Vandenberg but after California made them conduct a study on the effect of sonic booms on seals I bet they aren't willing to see what else they will make them do for hop test. Also, Brownsville is close to their R&D facility in McGregor, Texas which all the Raptor engines are tested and where they did the Grasshopper and F9 hop tests. So it's probably easier to keep them closer for testing. McGregor is also closer to Cocoa than Vandenberg and Florida is their primary launch site so it makes sense to also be building one there, yet after passing where they are building that one, I can't see any easy way to get it out. That won't anger the neighbors.