The main problem for this type of project is getting environmental and safety clearance and land rights. A particular problem with building in California is that the government there has pushed hard on their questionable HSR project and they might not want competition. There is also now a set of people who have a vested interest in keeping HSR going and won't like the idea of scrapping HSR for hyperloop.

On the other hand, Musk seems to have a lot of clout in California, so maybe it makes more sense to make his push there. If it doesn't work out for California, I hope he or someone else gets the project rolling somewhere. Texas might be a good candidate, since it has a fast-increasing population and is generally more pro-development than California.