weather in september

It is more than a bit rainy. Sept. is the rainiest month. The town will be real quiet and you will most likely find some of the restaurants closed for vacation/maintenence. The rainy season is generally over by the middle of Oct.

Would/do I go down during Sept. YES!!!!!

I have been to PV at various times of the year. September is the slow season and it is hot and VERY humid. Yeah, it rains on occasions but the rain is very refreshing. Some restaurants are closed but there are still many good ones to go to. Probably a better time to bargain for souvenirs and such as fewer people are in Vallarta. I say go for it!!! Vallarta is great any time of year.