I'm from Melbourne and there is a great meetup group here that we go to monthly. Just google Melbourne Chihuahua meetup and join the group. We meet at parks and dog friendly beaches around the city, occasionally meetups are held a bit further out such as in the dandenong ranges. Last weekend we had about 25 chihuahuas at the Altona dog beach and everyone had a blast.
Thanks Jan896 for my cute siggy!