We usually go the 3rd week of March, as that is when our two boys have their school vacation. We usually expect the highs to be in the mid 70s, sometimes in the 80s, but the evenings are usually cool, in the low 50s. A few times the lows got in the upper 40s. (Certainly beats the weather at home in CT). This past March we were lucky and had temps in the low 90s during the day, and mid 60s at night, but this was not the ordinary.
When we go out on the evening, we always bring a sweater or light jacket, unless the weather person says otherwise.