While I live a bit further south, these are generally speaking as anything can happen and the weather is pretty unpredictable but:
It's generally cooler, though not cold (though it can be at times, it was this year) and usually doesn't rain much in the month of March. Of course, this could change a bit if you were going in the end of the month, rather than the beginning (colder towards the start, and warms as the month moves on) .. though maybe someone thats gone during March can give you a better idea.
EDIT: looking at the month of March on weather.com shows no recorded rain at all during the whole month. the general temps seem to be a hi of 80ish (though remember, it could get cooler sometimes as low as 60) and a low of 50 (though it can get into the 30s) .. so, bring mostly "warm" clothes, with some cool clothes incase.