I was shocked to hear tha during December, there were well over 500 vehicles inside Yala on certain days, causing massive traffic jams inside the park.
Traffic has never reached this peak for the last 35 years or as far as I can remember, and a few years back even 50 vehicles were considered gross overcrowding. Needless to say, the massive crowds scared away the leopards (which everyone wants to see!) during this period, and drove them more into the brush. Unfortunately, the leopards who had no fear of the vehicles until this mad rush started, start getting fearful of the revving engines, loud talking and shouting, and ruckus it creates. They could well move permanantly into an area away from the roads where they could not be observed.
Also during this period, visitors could be seen climbing on the sides of jeeps, overtaking slow vehicles by going off road, and even standing on top of vehicles to see over the big crowd. All these are violations that need to stop.
So, my advise to you is to avoid Yala during school vacation time and the weekends, as you will see nothing.
As I have predicted before, the end to Yala being a destination to see animals is drawing closer, unless the governement (greedy for money this mass influx provides) restricts the number of vehicles into the park. I know that several Sri Lankan wild life lovers share the same concern that I do, with many avoiding even visiting Yala.