Hi,
I have almost the same offer, or maybe exactly the same offer, - something about $2k/month. Since I am literally from the opposite side of the Earth, I don't know how much it is for the life in SB (and in other parts of America as well), but as far as I know it is a typical funding package for American graduate students.
There is another thing I am wondering about - I am confused a bit about university rankings: while Times (20 in Eng&Tech worldwide) and phds.org (5-16 in ME) rank UCSB pretty high and USN places it on 26 in ME and on 19 in Eng (which also seems not bad) - QS ranks it only as 151-200 in mechanical engineering.