You should go to SF
the fingerprinting is done at another building than the INS office, two blocks uphill, in the intersection of Sansome and Broadway.
We went there and did FP two weeks early, with no problem.
They told that since they started using the new machines for fingerprinting, there is very little risk of having to do the FP twice. THe machines will tell immediately if the FP is not good.
Best of all, the INS people at that office are actually angels. You should see it to believe it.