I would focus on becoming as noticed as possible. You may even want to find a niche for yourself, which is a great way for people to remember you. For example, when I think of an app designer, I immediately think of Nathan Barry (author of the App Design Handbook, among other things). Building that reputation will be worth a lot!
As far as prep work goes, freelancing and building your own apps/projects is a great option. You get to LEARN by taking on interesting projects, NETWORK with professionals that lead to more opportunities, and earn MONEY.
Should I give calls and look for a job before moving
If it's a specific job, then yes! Communicate with the company/team and get to know them. Instead of saying, "I'm aperture and I would like to apply," say, "Hi! Your project is great and I really love what you are doing with it." You are essentially introducing yourself. They will most likely remember that - especially if they are a smaller company.
is silicon valley really the only place to look to?
SV is an amazing place filled with amazing people, but it is not the only place to look into. There are many tech hubs in California. Find out what you can afford, and what amenities you want from your city/town. Do you like being close to the beach (San Diego)? Do you like living in a fast-paced city (Los Angeles)? Would you like a view of the mountains (Mountain View)? If you have some time off, visit each place you're interested in for a week or so to get a feel of what they're like.
