There is a big celebration today, Sunday the 13th, in Thai Town in East Hollywood. It is not like in Thailand though, with people dumping water on everyone. This is more for farang to come and get a glimpse of Thai culture, and perhaps buy some stuff
I was there last night and got hit with some water after midnight. Some people play around with water fights but I don't think the majority of the farangs here are going to be friendly after they get splashed.