It depends on the area of the country- but it runs from end of Feb until early April.
When you say kids do you mean little kids on family vacations or are you talking about College Spring Breakers- the Cancun area is number 1 choice of resorts for them, they are aged 18-30 and it is a very boisterous time,parties and drinking being the main attraction, not something you'd want to spend a family holiday in the midst of.

Thanks Emdia. It was the 18-30's that I was concerned about. I'm not on a family holiday but I am going to just crash and relax to recharge my batteries. Not possible if there is a group intent on having a livelier time. Back to the drawing board.

I believe the Iberostar resorts on the Riviera Maya "strongly discourage" spring break groups, though I'm not sure how they actually enforce that.

We stayed at an Iberostar at Easter and saw no evidence of spring breakers and I get the impression they mostly prefer the action of Cancun .

To discourage Spring Breakers they won't accept reservations from anyone under 25 during those weeks.