No matter where the pool is located, if it is unheated and the temps get down into the mid-40's and low 50's at night....the water will be fairly cool even for kids. We stayed a few uears agp in LBV at the old RI by Marriott that was recently torn down in mid-October and the pool was unheated and it fairly chilly. The October and March temps in Orlando are comparable. I am not saying that you can't swim in an unheated pool in March but it will be chilly. But as we all know, when it comes to kids...they can usually endure much more than adults. If you don't think that you will have that much time for swimming anyway....I would not let the lack of an unheated pool stop me from staying if everything else is okay. The only question I would ask would be is whether the pool will have been opened for the season and whether it is being cleaned and serviced in March.