We'll be going down on March 15th and the forecast is definately for cooler weather than normal for March -- highs around 70s like you say (average highs are 78 0r 79 in March for the Orlando area). For me highs inthe 70s means jeans/T-shirt weather with a sweatshirt for the morning and a fleece jacket for at night. The sun plays a huge factor in how warm or cold you feel, and whether that sweatshirt or fleece is on or off. Shorts, though, and a swim suit take very little space. I'll take a two pair and a swimsuit just in case. The weather can change quickly. We had very similar weather temperature in the summer in Victoria, B.C. on a recent trip we took, and it is pleasant for touring, especially if there is sun.