Spring Break here is really not a crazy party scene at all. We have limited night life and a majority of the visitors (with exception to cruise ship passengers) are here to dive.
Cancun and Playa del Carmen are more attractive to the college spring breakers. We just don't have enough night life for them.
I will tell you however, that hotels and dive shops are busy in March because many people are able to travel with their children being out of school...so there are many family vacationers here in March.
March/Spring Break is NOT the busiest time however. Carnaval week (20th - 29th of February) is the busiest time with Thanksgiving week and the week between Christmas and New year's following. Spring break would fall behind those weeks.
Book your reservations now if you want to get in with the dive operator of your choice!
Have fun!