Well, the 15th of March is really pushing it for high numbers of specs in Galveston. It is not likely you will find any schooling action then. The schooling is triggered by the shrimp migrations and March 15 is just too early for that.
Sorry to say, but also that isn't a prime time for pier fishing for specs either, but you can certainly try that. Get live bait, shrimp or even crookers if you can find them and fish them under a popping cork. If the specs don't show, its likely that some other early species will show up to keep things interesting such as an early Mackeral run which isn't out of the realm of possibility.
Another possibility, assuming you are afoot and without a boat, is to walk the jetties, preferably the South, and take your live bait with you. You might be able to find some good fish out there at that time but it is kind of hit or miss that early.