Live in Florida and working in ca on a temporary basis, employer reimburses living expenses, do I have to pay ca state taxes

As you're working in CA, any income you make from that work is taxable to the state of CA. as a nonresident( because yoour home state is Florida). If your gross income or adjusted gross income, agi, is more than the amount for your filing status, age, and number of dependents, then you have a filing requirement. For example, as either a single or an HOH under 65 Y.O. with 1 dependent, you need to file your state tax return if the amount of your goross income is over$17,889 ( over $14,965 for your AGI) as of Dec. 31 2009.
The state income taxes that you paid in Ca are subject to tax deduction against your Federal tax return.(You must file a 1040 Schedule A, Itemized Deductions in order to claim either state income tax or state sales tax on your return.)

Any income earned while present in a state is taxable in that state. If you live in CA for limited period, you are part year resident of CA.