Is it good timing travel to Perth, Australia in March?

Only if you like it HOT.
It will be the end of summer then and very warm, but nice.

Depends where you are coming from, really...

Perfect time the big heat should have finished but still lovely warm days a few balmy nights but probably cooler in the evening . you get a nice sea breeze come through in the afternoons. Summer is dec jan feb

i don't see any problem with it. the weather would be nice and cool by then..

Yes I first came here for a holiday in March 2008 but it is still quite hot. around 30c every day.

If you like the weather to be warm and sunny, then perfect. The days could be around 28-34 degrees C and the nights just beautiful. It will be swimming weather but not too hot.

It depends if you like the warm weather. In March it is still around 30 degrees each day but it cools down in April. If your not used to the hot weather i think it would be best to go in April.