Should I move to Palo Alto. I live in the UK.

Next chirstmas I would have enough money to move to the USA. I am wondering if I should wait a year and move to the USA or wait a year and a half but move to Silicon Valley.

Do you have friends there?

No. There are plenty of challenges in the UK to keep you satisfied.

UK may not have the prestige of Palo Alto, but were not big on showing off either. There is a lot of cool stuff happening here.

You can't just move there. You need a H1-B visa. Which you get by being sponsored by an employer for a specific job that can not be filled by an American. Then, you can reside there as long as you are employed. To move to the states, you need to be top 5% material. It's possible, but it may take years of preparation until an opportunity arises.
Unless you have 500K and can create a minimum of 4 jobs for Americans which will enable you to get another type of visa.

I think programmers who move to Silicon Valley without having a real job offer are the equivalent of actors moving to LA thinking they're just going to break into the movie business.

Get good at what you're doing wherever it is that you're able to do that, and the talent scouts will always find you.