Q: Looking to live in California for 4 months and want to get work in bars and shops (if that makes any difference?)
A: You won't get a visa to do casual work such as bar work. You would have to be sponsored by a company who could not find a suitable American to fill the role. Your best chance would be through the 'Work America' scheme, where there is a reciprocal agreement between the US and UK to give a single years work visa to a certain number each year. You'll have to plan ahead, and meet certain criteria, (ie. age. I think 30 is the maximum). Search the internet for 'work america' or try http://www.bunac.co.uk