Like Canada you can tweak the amount of deductions on your paystub but you'll owe the same amount in the end. You'll file both US and Canadian taxes for 2011 which is slightly complex but you won't get double-taxes for the most part.
You'll pay roughly 6% CA state tax, 15% US federal tax plus medicare and a few other small items that I never know how to calculate.
As for places to live, ye olde Craigslist or your university housing service if interns from your school regularly get jobs in the valley.